feat(pos): add multi-language i18n (#37) and multi-currency USD/MXN (#38)

- i18n.js with 130+ translation keys for es/en, loaded in all 11 templates
- sidebar.js uses t() for all nav labels, adds MX/US language toggle
- app-init.js role labels use i18n
- currency.py service with convert() and format_currency()
- config.py adds DEFAULT_CURRENCY and EXCHANGE_RATE_USD_MXN settings
- config_bp.py adds GET/PUT /pos/api/config/currency endpoints
- config.html adds currency/exchange-rate section (Section 8)
- config.js adds loadCurrency/saveCurrency with localStorage sync
- pos.js fmt() reads pos_currency from localStorage for USD/MXN display

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pos/config.py

@@ -36,3 +36,7 @@ SMTP_FROM = os.environ.get('SMTP_FROM', 'noreply@nexusautoparts.com')
 WHATSAPP_TOKEN = os.environ.get("WHATSAPP_TOKEN", "")
 WHATSAPP_PHONE_ID = os.environ.get("WHATSAPP_PHONE_ID", "")
 WHATSAPP_VERIFY_TOKEN = os.environ.get("WHATSAPP_VERIFY_TOKEN", "nexus-wa-verify-2026")
+
+# Multi-currency
+DEFAULT_CURRENCY = os.environ.get('DEFAULT_CURRENCY', 'MXN')
+EXCHANGE_RATE_USD_MXN = float(os.environ.get('EXCHANGE_RATE_USD_MXN', '17.5'))

pos/services/currency.py

@@ -0,0 +1,55 @@
+"""Multi-currency support for border refaccionarias.
+
+Supports MXN and USD with configurable exchange rate.
+"""
+
+from config import DEFAULT_CURRENCY, EXCHANGE_RATE_USD_MXN
+
+CURRENCIES = {
+    'MXN': {'symbol': '$', 'name': 'Peso Mexicano', 'name_en': 'Mexican Peso', 'decimals': 2},
+    'USD': {'symbol': 'US$', 'name': 'Dolar Estadounidense', 'name_en': 'US Dollar', 'decimals': 2},
+}
+
+
+def convert(amount, from_currency, to_currency, rate=None):
+    """Convert an amount between currencies.
+
+    Args:
+        amount: The numeric amount to convert.
+        from_currency: Source currency code ('MXN' or 'USD').
+        to_currency: Target currency code ('MXN' or 'USD').
+        rate: Optional custom exchange rate (USD->MXN). Defaults to config value.
+
+    Returns:
+        The converted amount, rounded to 2 decimals.
+    """
+    if from_currency == to_currency:
+        return amount
+    if rate is None:
+        rate = EXCHANGE_RATE_USD_MXN
+    if from_currency == 'USD' and to_currency == 'MXN':
+        return round(amount * rate, 2)
+    if from_currency == 'MXN' and to_currency == 'USD':
+        return round(amount / rate, 2)
+    return amount
+
+
+def format_currency(amount, currency='MXN'):
+    """Format an amount with the appropriate currency symbol.
+
+    Args:
+        amount: Numeric value.
+        currency: Currency code.
+
+    Returns:
+        Formatted string like '$1,234.56' or 'US$1,234.56'.
+    """
+    info = CURRENCIES.get(currency, CURRENCIES['MXN'])
+    return f"{info['symbol']}{amount:,.{info['decimals']}f}"
+
+
+def get_currency_info(code=None):
+    """Return currency metadata dict. If code is None, return all."""
+    if code:
+        return CURRENCIES.get(code)
+    return CURRENCIES

pos/static/js/app-init.js

@@ -40,9 +40,10 @@
 
     var name = employee.name || payload.name || 'Usuario';
     var role = employee.role || payload.role || '';
+    var _t = typeof window.t === 'function' ? window.t : function(k) { return k; };
     var roleLabels = {
-        'owner': 'Dueño', 'admin': 'Administrador', 'cashier': 'Cajero',
-        'warehouse': 'Almacén', 'accountant': 'Contador'
+        'owner': _t('role_owner'), 'admin': _t('role_admin'), 'cashier': _t('role_cashier'),
+        'warehouse': _t('role_warehouse'), 'accountant': _t('role_accountant')
     };
     var roleLabel = roleLabels[role] || role;
     var initials = name.split(' ').map(function(p) { return p[0]; }).join('').toUpperCase().substring(0, 2);

pos/static/js/config.js

@@ -416,6 +416,68 @@ const Config = (() => {
         });
     }
 
+    // -------------------------------------------------------------------------
+    // Currency
+    // -------------------------------------------------------------------------
+    async function loadCurrency() {
+        try {
+            var res = await fetch(API + '/currency', { headers: headers() });
+            if (!res.ok) return;
+            var d = await res.json();
+            var selCurrency = document.getElementById('cfg-currency');
+            var inpRate = document.getElementById('cfg-exchange-rate');
+            if (selCurrency) selCurrency.value = d.currency || 'MXN';
+            if (inpRate) inpRate.value = d.exchange_rate || 17.5;
+            // Store in localStorage for POS fmt() to pick up
+            localStorage.setItem('pos_currency', d.currency || 'MXN');
+            localStorage.setItem('pos_exchange_rate', d.exchange_rate || 17.5);
+        } catch (e) {
+            console.error('Config.loadCurrency:', e);
+        }
+    }
+
+    async function saveCurrency() {
+        var selCurrency = document.getElementById('cfg-currency');
+        var inpRate = document.getElementById('cfg-exchange-rate');
+        var statusEl = document.getElementById('currency-status');
+        var btn = document.getElementById('btn-save-currency');
+
+        if (!selCurrency || !inpRate) return;
+
+        var currency = selCurrency.value;
+        var rate = parseFloat(inpRate.value);
+
+        if (!rate || rate <= 0) {
+            toast('Tipo de cambio invalido', 'error');
+            return;
+        }
+
+        if (btn) { btn.disabled = true; btn.textContent = 'Guardando...'; }
+
+        try {
+            var res = await fetch(API + '/currency', {
+                method: 'PUT',
+                headers: headers(),
+                body: JSON.stringify({ currency: currency, exchange_rate: rate })
+            });
+            if (!res.ok) {
+                var err = await res.json().catch(function() { return { error: res.statusText }; });
+                throw new Error(err.error || 'Save failed');
+            }
+            localStorage.setItem('pos_currency', currency);
+            localStorage.setItem('pos_exchange_rate', rate);
+            toast('Moneda actualizada');
+            if (statusEl) statusEl.textContent = currency + ' — TC: ' + rate;
+        } catch (e) {
+            toast(e.message, 'error');
+        } finally {
+            if (btn) {
+                btn.disabled = false;
+                btn.textContent = 'Guardar Moneda';
+            }
+        }
+    }
+
     // -------------------------------------------------------------------------
     // Init
     // -------------------------------------------------------------------------
@@ -441,6 +503,7 @@ const Config = (() => {
         loadBranches();
         loadEmployees();
         loadBusiness();
+        loadCurrency();
     }
 
     document.addEventListener('DOMContentLoaded', init);
@@ -448,6 +511,7 @@ const Config = (() => {
     return {
         init, setTheme, selectThemeOption,
         loadBranches, loadEmployees, saveBranch, saveEmployee,
+        loadCurrency, saveCurrency,
         openModal, closeModal
     };
 })();

pos/static/js/i18n.js

@@ -0,0 +1,342 @@
+/**
+ * i18n.js — Simple internationalization for Nexus Autoparts POS
+ * Supports: es (Spanish/Mexico) and en (English/USA)
+ */
+var I18N = {
+  es: {
+    // Sidebar nav
+    'dashboard': 'Dashboard',
+    'pos': 'Punto de Venta',
+    'catalog': 'Catalogo',
+    'inventory': 'Inventario',
+    'customers': 'Clientes',
+    'invoicing': 'Facturacion',
+    'accounting': 'Contabilidad',
+    'reports': 'Reportes',
+    'fleet': 'Flotillas',
+    'whatsapp': 'WhatsApp',
+    'config': 'Configuracion',
+    // Sidebar sections
+    'nav_main': 'Principal',
+    'nav_management': 'Gestion',
+    'nav_system': 'Sistema',
+    // Common actions
+    'search': 'Buscar',
+    'save': 'Guardar',
+    'cancel': 'Cancelar',
+    'delete': 'Eliminar',
+    'edit': 'Editar',
+    'new': 'Nuevo',
+    'close': 'Cerrar',
+    'confirm': 'Confirmar',
+    'back': 'Regresar',
+    'next': 'Siguiente',
+    'print': 'Imprimir',
+    'export': 'Exportar',
+    'import': 'Importar',
+    'refresh': 'Actualizar',
+    'loading': 'Cargando...',
+    'no_results': 'Sin resultados',
+    'error': 'Error',
+    'success': 'Exito',
+    'warning': 'Advertencia',
+    // Financial
+    'total': 'Total',
+    'subtotal': 'Subtotal',
+    'tax': 'IVA',
+    'price': 'Precio',
+    'unit_price': 'Precio Unitario',
+    'cost': 'Costo',
+    'discount': 'Descuento',
+    'margin': 'Margen',
+    'profit': 'Utilidad',
+    'balance': 'Saldo',
+    'amount': 'Monto',
+    // Inventory
+    'quantity': 'Cantidad',
+    'stock': 'Existencias',
+    'min_stock': 'Minimo',
+    'max_stock': 'Maximo',
+    'sku': 'SKU',
+    'barcode': 'Codigo de Barras',
+    'brand': 'Marca',
+    'category': 'Categoria',
+    'description': 'Descripcion',
+    'location': 'Ubicacion',
+    // Table headers
+    'name': 'Nombre',
+    'date': 'Fecha',
+    'status': 'Estado',
+    'actions': 'Acciones',
+    'id': 'ID',
+    'type': 'Tipo',
+    'notes': 'Notas',
+    // POS
+    'charge': 'Cobrar',
+    'quote': 'Cotizacion',
+    'layaway': 'Apartado',
+    'credit': 'Credito',
+    'cash': 'Efectivo',
+    'transfer': 'Transferencia',
+    'card': 'Tarjeta',
+    'mixed': 'Mixto',
+    'change': 'Cambio',
+    'customer': 'Cliente',
+    'general_public': 'Publico General',
+    'sale': 'Venta',
+    'sales': 'Ventas',
+    'ticket': 'Ticket',
+    'receipt': 'Recibo',
+    'payment': 'Pago',
+    'payment_method': 'Metodo de Pago',
+    'add_to_cart': 'Agregar',
+    'clear_cart': 'Limpiar Carrito',
+    'hold_sale': 'Pausar Venta',
+    'recall_sale': 'Retomar Venta',
+    'cancel_sale': 'Cancelar Venta',
+    'confirm_payment': 'Confirmar Pago',
+    'cash_received': 'Efectivo Recibido',
+    'amount_due': 'Total a Pagar',
+    'remaining': 'Faltante',
+    // Customers
+    'phone': 'Telefono',
+    'email': 'Correo',
+    'address': 'Direccion',
+    'rfc': 'RFC',
+    'credit_limit': 'Limite de Credito',
+    'credit_balance': 'Saldo de Credito',
+    'price_tier': 'Nivel de Precio',
+    // Invoicing
+    'invoice': 'Factura',
+    'cfdi': 'CFDI',
+    'stamp': 'Timbrar',
+    'cancel_invoice': 'Cancelar Factura',
+    // Config
+    'appearance': 'Apariencia',
+    'business_data': 'Datos de la Empresa',
+    'employees': 'Empleados',
+    'printers': 'Impresoras',
+    'branches': 'Sucursales',
+    'fiscal_params': 'Parametros Fiscales',
+    'system_prefs': 'Preferencias del Sistema',
+    'currency_config': 'Moneda',
+    'language': 'Idioma',
+    'theme': 'Tema',
+    'dark_theme': 'Tema oscuro',
+    'light_theme': 'Tema claro',
+    'logout': 'Cerrar sesion',
+    // Currency
+    'currency': 'Moneda',
+    'exchange_rate': 'Tipo de Cambio',
+    'default_currency': 'Moneda Predeterminada',
+    'mxn': 'Peso Mexicano',
+    'usd': 'Dolar Estadounidense',
+    // Roles
+    'role_owner': 'Dueno',
+    'role_admin': 'Administrador',
+    'role_cashier': 'Cajero',
+    'role_warehouse': 'Almacen',
+    'role_accountant': 'Contador',
+    // Reports
+    'daily_sales': 'Ventas del Dia',
+    'weekly_sales': 'Ventas de la Semana',
+    'monthly_sales': 'Ventas del Mes',
+    'top_products': 'Productos Mas Vendidos',
+    'low_stock': 'Bajo Stock',
+    // Fleet
+    'vehicle': 'Vehiculo',
+    'plate': 'Placa',
+    'vin': 'VIN',
+    'mileage': 'Kilometraje',
+    // Misc
+    'yes': 'Si',
+    'no': 'No',
+    'all': 'Todos',
+    'active': 'Activo',
+    'inactive': 'Inactivo',
+    'pending': 'Pendiente',
+    'completed': 'Completado',
+    'cancelled': 'Cancelado',
+  },
+  en: {
+    // Sidebar nav
+    'dashboard': 'Dashboard',
+    'pos': 'Point of Sale',
+    'catalog': 'Catalog',
+    'inventory': 'Inventory',
+    'customers': 'Customers',
+    'invoicing': 'Invoicing',
+    'accounting': 'Accounting',
+    'reports': 'Reports',
+    'fleet': 'Fleet',
+    'whatsapp': 'WhatsApp',
+    'config': 'Settings',
+    // Sidebar sections
+    'nav_main': 'Main',
+    'nav_management': 'Management',
+    'nav_system': 'System',
+    // Common actions
+    'search': 'Search',
+    'save': 'Save',
+    'cancel': 'Cancel',
+    'delete': 'Delete',
+    'edit': 'Edit',
+    'new': 'New',
+    'close': 'Close',
+    'confirm': 'Confirm',
+    'back': 'Back',
+    'next': 'Next',
+    'print': 'Print',
+    'export': 'Export',
+    'import': 'Import',
+    'refresh': 'Refresh',
+    'loading': 'Loading...',
+    'no_results': 'No results',
+    'error': 'Error',
+    'success': 'Success',
+    'warning': 'Warning',
+    // Financial
+    'total': 'Total',
+    'subtotal': 'Subtotal',
+    'tax': 'Tax',
+    'price': 'Price',
+    'unit_price': 'Unit Price',
+    'cost': 'Cost',
+    'discount': 'Discount',
+    'margin': 'Margin',
+    'profit': 'Profit',
+    'balance': 'Balance',
+    'amount': 'Amount',
+    // Inventory
+    'quantity': 'Quantity',
+    'stock': 'Stock',
+    'min_stock': 'Minimum',
+    'max_stock': 'Maximum',
+    'sku': 'SKU',
+    'barcode': 'Barcode',
+    'brand': 'Brand',
+    'category': 'Category',
+    'description': 'Description',
+    'location': 'Location',
+    // Table headers
+    'name': 'Name',
+    'date': 'Date',
+    'status': 'Status',
+    'actions': 'Actions',
+    'id': 'ID',
+    'type': 'Type',
+    'notes': 'Notes',
+    // POS
+    'charge': 'Charge',
+    'quote': 'Quote',
+    'layaway': 'Layaway',
+    'credit': 'Credit',
+    'cash': 'Cash',
+    'transfer': 'Transfer',
+    'card': 'Card',
+    'mixed': 'Mixed',
+    'change': 'Change',
+    'customer': 'Customer',
+    'general_public': 'Walk-in Customer',
+    'sale': 'Sale',
+    'sales': 'Sales',
+    'ticket': 'Ticket',
+    'receipt': 'Receipt',
+    'payment': 'Payment',
+    'payment_method': 'Payment Method',
+    'add_to_cart': 'Add',
+    'clear_cart': 'Clear Cart',
+    'hold_sale': 'Hold Sale',
+    'recall_sale': 'Recall Sale',
+    'cancel_sale': 'Cancel Sale',
+    'confirm_payment': 'Confirm Payment',
+    'cash_received': 'Cash Received',
+    'amount_due': 'Amount Due',
+    'remaining': 'Remaining',
+    // Customers
+    'phone': 'Phone',
+    'email': 'Email',
+    'address': 'Address',
+    'rfc': 'Tax ID (RFC)',
+    'credit_limit': 'Credit Limit',
+    'credit_balance': 'Credit Balance',
+    'price_tier': 'Price Tier',
+    // Invoicing
+    'invoice': 'Invoice',
+    'cfdi': 'CFDI',
+    'stamp': 'Stamp',
+    'cancel_invoice': 'Cancel Invoice',
+    // Config
+    'appearance': 'Appearance',
+    'business_data': 'Business Info',
+    'employees': 'Employees',
+    'printers': 'Printers',
+    'branches': 'Branches',
+    'fiscal_params': 'Tax Settings',
+    'system_prefs': 'System Preferences',
+    'currency_config': 'Currency',
+    'language': 'Language',
+    'theme': 'Theme',
+    'dark_theme': 'Dark theme',
+    'light_theme': 'Light theme',
+    'logout': 'Log out',
+    // Currency
+    'currency': 'Currency',
+    'exchange_rate': 'Exchange Rate',
+    'default_currency': 'Default Currency',
+    'mxn': 'Mexican Peso',
+    'usd': 'US Dollar',
+    // Roles
+    'role_owner': 'Owner',
+    'role_admin': 'Administrator',
+    'role_cashier': 'Cashier',
+    'role_warehouse': 'Warehouse',
+    'role_accountant': 'Accountant',
+    // Reports
+    'daily_sales': 'Daily Sales',
+    'weekly_sales': 'Weekly Sales',
+    'monthly_sales': 'Monthly Sales',
+    'top_products': 'Top Products',
+    'low_stock': 'Low Stock',
+    // Fleet
+    'vehicle': 'Vehicle',
+    'plate': 'Plate',
+    'vin': 'VIN',
+    'mileage': 'Mileage',
+    // Misc
+    'yes': 'Yes',
+    'no': 'No',
+    'all': 'All',
+    'active': 'Active',
+    'inactive': 'Inactive',
+    'pending': 'Pending',
+    'completed': 'Completed',
+    'cancelled': 'Cancelled',
+  }
+};
+
+var currentLang = localStorage.getItem('pos_lang') || 'es';
+
+/**
+ * Translate a key to the current language.
+ * Falls back to Spanish, then to the raw key.
+ */
+window.t = function(key) {
+  return (I18N[currentLang] && I18N[currentLang][key]) || (I18N['es'] && I18N['es'][key]) || key;
+};
+
+/**
+ * Switch the UI language and reload.
+ */
+window.setLang = function(lang) {
+  currentLang = lang;
+  localStorage.setItem('pos_lang', lang);
+  location.reload();
+};
+
+/**
+ * Get the current language code.
+ */
+window.getLang = function() {
+  return currentLang;
+};

pos/static/js/sidebar.js

@@ -1,34 +1,39 @@
 /**
  * sidebar.js — Shared sidebar matching the design system style
  * Replaces existing sidebar in each page with a consistent, themed version.
+ * Uses i18n t() for all labels when available.
  */
 (function() {
     'use strict';
 
+    // i18n helper — falls back to raw string if i18n.js not loaded
+    var _t = typeof window.t === 'function' ? window.t : function(k) { return k; };
+
     var u = window.POS_USER || {};
     var name = u.name || 'Usuario';
     var roleLabel = u.roleLabel || '';
     var initials = u.initials || '?';
     var currentPath = window.location.pathname;
     var currentTheme = localStorage.getItem('pos_theme') || 'industrial';
+    var currentLang = localStorage.getItem('pos_lang') || 'es';
 
     var navSections = [
-        { label: 'Principal', items: [
-            { name: 'Dashboard', href: '/pos/dashboard', icon: '<rect x="3" y="3" width="7" height="7"/><rect x="14" y="3" width="7" height="7"/><rect x="14" y="14" width="7" height="7"/><rect x="3" y="14" width="7" height="7"/>' },
-            { name: 'POS', href: '/pos/sale', icon: '<rect x="2" y="3" width="20" height="14" rx="2"/><path d="M8 21h8M12 17v4"/>' },
-            { name: 'Catálogo', href: '/pos/catalog', icon: '<path d="M4 6h16M4 10h16M4 14h16M4 18h16"/>' },
-            { name: 'Inventario', href: '/pos/inventory', icon: '<path d="M21 16V8a2 2 0 0 0-1-1.73l-7-4a2 2 0 0 0-2 0l-7 4A2 2 0 0 0 3 8v8a2 2 0 0 0 1 1.73l7 4a2 2 0 0 0 2 0l7-4A2 2 0 0 0 21 16z"/><polyline points="3.27 6.96 12 12.01 20.73 6.96"/><line x1="12" y1="22.08" x2="12" y2="12"/>' },
+        { label: _t('nav_main'), items: [
+            { name: _t('dashboard'), href: '/pos/dashboard', icon: '<rect x="3" y="3" width="7" height="7"/><rect x="14" y="3" width="7" height="7"/><rect x="14" y="14" width="7" height="7"/><rect x="3" y="14" width="7" height="7"/>' },
+            { name: _t('pos'), href: '/pos/sale', icon: '<rect x="2" y="3" width="20" height="14" rx="2"/><path d="M8 21h8M12 17v4"/>' },
+            { name: _t('catalog'), href: '/pos/catalog', icon: '<path d="M4 6h16M4 10h16M4 14h16M4 18h16"/>' },
+            { name: _t('inventory'), href: '/pos/inventory', icon: '<path d="M21 16V8a2 2 0 0 0-1-1.73l-7-4a2 2 0 0 0-2 0l-7 4A2 2 0 0 0 3 8v8a2 2 0 0 0 1 1.73l7 4a2 2 0 0 0 2 0l7-4A2 2 0 0 0 21 16z"/><polyline points="3.27 6.96 12 12.01 20.73 6.96"/><line x1="12" y1="22.08" x2="12" y2="12"/>' },
         ]},
-        { label: 'Gestión', items: [
-            { name: 'Clientes', href: '/pos/customers', icon: '<path d="M17 21v-2a4 4 0 0 0-4-4H5a4 4 0 0 0-4 4v2"/><circle cx="9" cy="7" r="4"/><path d="M23 21v-2a4 4 0 0 0-3-3.87M16 3.13a4 4 0 0 1 0 7.75"/>' },
-            { name: 'Facturación', href: '/pos/invoicing', icon: '<path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z"/><polyline points="14 2 14 8 20 8"/><line x1="16" y1="13" x2="8" y2="13"/><line x1="16" y1="17" x2="8" y2="17"/><polyline points="10 9 9 9 8 9"/>' },
-            { name: 'Contabilidad', href: '/pos/accounting', icon: '<line x1="12" y1="1" x2="12" y2="23"/><path d="M17 5H9.5a3.5 3.5 0 0 0 0 7h5a3.5 3.5 0 0 1 0 7H6"/>' },
-            { name: 'Reportes', href: '/pos/reports', icon: '<line x1="18" y1="20" x2="18" y2="10"/><line x1="12" y1="20" x2="12" y2="4"/><line x1="6" y1="20" x2="6" y2="14"/>' },
-            { name: 'Flotillas', href: '/pos/fleet', icon: '<path d="M1 13h22M1 13l2-6h6l2 6M9 7h6l2 6M15 13l2-6M5 17a2 2 0 1 0 0-4 2 2 0 0 0 0 4zM19 17a2 2 0 1 0 0-4 2 2 0 0 0 0 4z"/>' },
-            { name: 'WhatsApp', href: '/pos/whatsapp', icon: '<path d="M21 11.5a8.38 8.38 0 0 1-.9 3.8 8.5 8.5 0 0 1-7.6 4.7 8.38 8.38 0 0 1-3.8-.9L3 21l1.9-5.7a8.38 8.38 0 0 1-.9-3.8 8.5 8.5 0 0 1 4.7-7.6 8.38 8.38 0 0 1 3.8-.9h.5a8.48 8.48 0 0 1 8 8v.5z"/>' },
+        { label: _t('nav_management'), items: [
+            { name: _t('customers'), href: '/pos/customers', icon: '<path d="M17 21v-2a4 4 0 0 0-4-4H5a4 4 0 0 0-4 4v2"/><circle cx="9" cy="7" r="4"/><path d="M23 21v-2a4 4 0 0 0-3-3.87M16 3.13a4 4 0 0 1 0 7.75"/>' },
+            { name: _t('invoicing'), href: '/pos/invoicing', icon: '<path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z"/><polyline points="14 2 14 8 20 8"/><line x1="16" y1="13" x2="8" y2="13"/><line x1="16" y1="17" x2="8" y2="17"/><polyline points="10 9 9 9 8 9"/>' },
+            { name: _t('accounting'), href: '/pos/accounting', icon: '<line x1="12" y1="1" x2="12" y2="23"/><path d="M17 5H9.5a3.5 3.5 0 0 0 0 7h5a3.5 3.5 0 0 1 0 7H6"/>' },
+            { name: _t('reports'), href: '/pos/reports', icon: '<line x1="18" y1="20" x2="18" y2="10"/><line x1="12" y1="20" x2="12" y2="4"/><line x1="6" y1="20" x2="6" y2="14"/>' },
+            { name: _t('fleet'), href: '/pos/fleet', icon: '<path d="M1 13h22M1 13l2-6h6l2 6M9 7h6l2 6M15 13l2-6M5 17a2 2 0 1 0 0-4 2 2 0 0 0 0 4zM19 17a2 2 0 1 0 0-4 2 2 0 0 0 0 4z"/>' },
+            { name: _t('whatsapp'), href: '/pos/whatsapp', icon: '<path d="M21 11.5a8.38 8.38 0 0 1-.9 3.8 8.5 8.5 0 0 1-7.6 4.7 8.38 8.38 0 0 1-3.8-.9L3 21l1.9-5.7a8.38 8.38 0 0 1-.9-3.8 8.5 8.5 0 0 1 4.7-7.6 8.38 8.38 0 0 1 3.8-.9h.5a8.48 8.48 0 0 1 8 8v.5z"/>' },
         ]},
-        { label: 'Sistema', items: [
-            { name: 'Configuración', href: '/pos/config', icon: '<circle cx="12" cy="12" r="3"/><path d="M19.07 4.93a10 10 0 0 1 0 14.14M4.93 4.93a10 10 0 0 0 0 14.14"/>' },
+        { label: _t('nav_system'), items: [
+            { name: _t('config'), href: '/pos/config', icon: '<circle cx="12" cy="12" r="3"/><path d="M19.07 4.93a10 10 0 0 1 0 14.14M4.93 4.93a10 10 0 0 0 0 14.14"/>' },
         ]},
     ];
 
@@ -51,14 +56,24 @@
 
     // Theme toggle buttons
     var themeHtml = '<div class="sidebar__theme-toggle">'
-        + '<button class="theme-toggle-btn' + (currentTheme === 'industrial' ? ' is-active' : '') + '" onclick="posSetTheme(\'industrial\');updateThemeButtons()" title="Tema oscuro">'
+        + '<button class="theme-toggle-btn' + (currentTheme === 'industrial' ? ' is-active' : '') + '" onclick="posSetTheme(\'industrial\');updateThemeButtons()" title="' + _t('dark_theme') + '">'
         + '<svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/></svg>'
         + '</button>'
-        + '<button class="theme-toggle-btn' + (currentTheme === 'modern' ? ' is-active' : '') + '" onclick="posSetTheme(\'modern\');updateThemeButtons()" title="Tema claro">'
+        + '<button class="theme-toggle-btn' + (currentTheme === 'modern' ? ' is-active' : '') + '" onclick="posSetTheme(\'modern\');updateThemeButtons()" title="' + _t('light_theme') + '">'
         + '<svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="12" cy="12" r="5"/><line x1="12" y1="1" x2="12" y2="3"/><line x1="12" y1="21" x2="12" y2="23"/><line x1="4.22" y1="4.22" x2="5.64" y2="5.64"/><line x1="18.36" y1="18.36" x2="19.78" y2="19.78"/><line x1="1" y1="12" x2="3" y2="12"/><line x1="21" y1="12" x2="23" y2="12"/><line x1="4.22" y1="19.78" x2="5.64" y2="18.36"/><line x1="18.36" y1="5.64" x2="19.78" y2="4.22"/></svg>'
         + '</button>'
         + '</div>';
 
+    // Language toggle buttons
+    var langHtml = '<div class="sidebar__lang-toggle">'
+        + '<button class="lang-toggle-btn' + (currentLang === 'es' ? ' is-active' : '') + '" onclick="setLang(\'es\')" title="Espanol">'
+        + '<span class="lang-flag">MX</span> ES'
+        + '</button>'
+        + '<button class="lang-toggle-btn' + (currentLang === 'en' ? ' is-active' : '') + '" onclick="setLang(\'en\')" title="English">'
+        + '<span class="lang-flag">US</span> EN'
+        + '</button>'
+        + '</div>';
+
     window.updateThemeButtons = function() {
         var t = localStorage.getItem('pos_theme') || 'industrial';
         document.querySelectorAll('.theme-toggle-btn').forEach(function(b, i) {
@@ -76,13 +91,14 @@
         + '</div>'
         + '<nav class="sidebar__nav">' + navHtml + '</nav>'
         + themeHtml
+        + langHtml
         + '<div class="sidebar__footer">'
         + '  <div class="sidebar__user-avatar">' + initials + '</div>'
         + '  <div class="sidebar__user-info">'
         + '    <div class="sidebar__user-name">' + name + '</div>'
         + '    <div class="sidebar__user-role">' + roleLabel + '</div>'
         + '  </div>'
-        + '  <button class="sidebar__logout-btn" onclick="posLogout()" title="Cerrar sesión">'
+        + '  <button class="sidebar__logout-btn" onclick="posLogout()" title="' + _t('logout') + '">'
         + '    <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4"/><polyline points="16 17 21 12 16 7"/><line x1="21" y1="12" x2="9" y2="12"/></svg>'
         + '  </button>'
         + '</div>';
@@ -110,10 +126,11 @@
         '.nav-item__icon{width:18px;height:18px;flex-shrink:0;opacity:0.7}',
         '.nav-item.is-active .nav-item__icon{opacity:1}',
 
-        '.sidebar__theme-toggle{display:flex;gap:4px;padding:8px 16px;border-top:1px solid var(--color-border)}',
-        '.theme-toggle-btn{flex:1;display:flex;align-items:center;justify-content:center;gap:6px;padding:6px;border:1px solid var(--color-border);border-radius:var(--radius-sm,4px);background:none;color:var(--color-text-muted);cursor:pointer;transition:all 0.15s;font-size:0.75rem}',
-        '.theme-toggle-btn:hover{color:var(--color-text-primary);background:var(--color-surface-2,rgba(255,255,255,0.04))}',
-        '.theme-toggle-btn.is-active{background:var(--color-primary-muted,rgba(245,166,35,0.12));color:var(--color-primary);border-color:var(--color-primary)}',
+        '.sidebar__theme-toggle,.sidebar__lang-toggle{display:flex;gap:4px;padding:8px 16px;border-top:1px solid var(--color-border)}',
+        '.theme-toggle-btn,.lang-toggle-btn{flex:1;display:flex;align-items:center;justify-content:center;gap:6px;padding:6px;border:1px solid var(--color-border);border-radius:var(--radius-sm,4px);background:none;color:var(--color-text-muted);cursor:pointer;transition:all 0.15s;font-size:0.75rem}',
+        '.theme-toggle-btn:hover,.lang-toggle-btn:hover{color:var(--color-text-primary);background:var(--color-surface-2,rgba(255,255,255,0.04))}',
+        '.theme-toggle-btn.is-active,.lang-toggle-btn.is-active{background:var(--color-primary-muted,rgba(245,166,35,0.12));color:var(--color-primary);border-color:var(--color-primary)}',
+        '.lang-flag{font-weight:700;font-size:0.625rem;letter-spacing:0.04em}',
 
         '.sidebar__footer{padding:var(--space-3,12px) var(--space-4,16px);border-top:1px solid var(--color-border);display:flex;align-items:center;gap:var(--space-2,8px)}',
         '.sidebar__user-avatar{width:28px;height:28px;border-radius:50%;background:var(--color-primary);color:var(--color-text-inverse,#fff);display:flex;align-items:center;justify-content:center;font-size:0.6875rem;font-weight:700;flex-shrink:0}',
@@ -124,7 +141,7 @@
         '.sidebar__logout-btn:hover{color:var(--color-error,#F85149);border-color:var(--color-error,#F85149)}',
 
         '.pos-main-offset{margin-left:260px}',
-        '@media(max-width:768px){.pos-sidebar{width:56px}.brand-name,.nav-item span,.sidebar__user-info,.nav-section-label,.sidebar__theme-toggle{display:none}.sidebar__brand{justify-content:center;padding:12px 8px}.sidebar__footer{flex-direction:column;padding:8px}.pos-main-offset{margin-left:56px}}',
+        '@media(max-width:768px){.pos-sidebar{width:56px}.brand-name,.nav-item span,.sidebar__user-info,.nav-section-label,.sidebar__theme-toggle,.sidebar__lang-toggle{display:none}.sidebar__brand{justify-content:center;padding:12px 8px}.sidebar__footer{flex-direction:column;padding:8px}.pos-main-offset{margin-left:56px}}',
     ].join('\n');
     document.head.appendChild(css);
 

pos/templates/accounting.html

@@ -2301,6 +2301,7 @@
     </div>
   </div>
 
+  <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
   <script src="/pos/static/js/accounting.js"></script>

pos/templates/catalog.html

@@ -737,6 +737,7 @@
     <button class="banner__dismiss" onclick="document.getElementById('offlineBanner').style.display='none'" aria-label="Cerrar">&times;</button>
   </div>
 
+  <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
   <script src="/pos/static/js/catalog.js"></script>

pos/templates/config.html

@@ -1702,6 +1702,44 @@
           </div>
         </div>
 
+        <!-- ===============================================================
+             SECTION 8: MONEDA / CURRENCY
+             =============================================================== -->
+        <div class="settings-section">
+          <div class="settings-section__header">
+            <div class="settings-section__icon">
+              <svg viewBox="0 0 24 24"><line x1="12" y1="1" x2="12" y2="23"/><path d="M17 5H9.5a3.5 3.5 0 0 0 0 7h5a3.5 3.5 0 0 1 0 7H6"/></svg>
+            </div>
+            <div>
+              <div class="settings-section__title" data-i18n="currency_config">Moneda</div>
+              <div class="settings-section__desc">Configura la moneda y tipo de cambio para ventas</div>
+            </div>
+          </div>
+
+          <div class="settings-card" style="padding:var(--space-5);">
+            <div class="form-grid" style="display:grid;grid-template-columns:1fr 1fr;gap:var(--space-4);">
+              <div class="form-group">
+                <label class="form-label" data-i18n="default_currency">Moneda Predeterminada</label>
+                <select class="form-input" id="cfg-currency" style="padding:var(--space-2) var(--space-3);border:1px solid var(--color-border);border-radius:var(--radius-sm,4px);background:var(--color-bg-base);color:var(--color-text-primary);font-size:var(--text-body-sm);">
+                  <option value="MXN">$ MXN — Peso Mexicano</option>
+                  <option value="USD">US$ USD — US Dollar</option>
+                </select>
+              </div>
+              <div class="form-group">
+                <label class="form-label" data-i18n="exchange_rate">Tipo de Cambio USD/MXN</label>
+                <input class="form-input" id="cfg-exchange-rate" type="number" step="0.01" min="0.01" value="17.50"
+                       style="padding:var(--space-2) var(--space-3);border:1px solid var(--color-border);border-radius:var(--radius-sm,4px);background:var(--color-bg-base);color:var(--color-text-primary);font-size:var(--text-body-sm);font-family:var(--font-mono);" />
+              </div>
+            </div>
+            <div style="margin-top:var(--space-4);display:flex;gap:var(--space-3);align-items:center;">
+              <button class="btn btn--primary" id="btn-save-currency" style="padding:var(--space-2) var(--space-4);font-size:var(--text-body-sm);" onclick="Config.saveCurrency()">
+                Guardar Moneda
+              </button>
+              <span id="currency-status" style="font-size:var(--text-caption);color:var(--color-text-muted);"></span>
+            </div>
+          </div>
+        </div>
+
       </div><!-- /content-scroll -->
     </main>
   </div><!-- /app-shell -->
@@ -1876,6 +1914,7 @@
     @keyframes slideUp { from { opacity: 0; transform: translateY(20px); } to { opacity: 1; transform: translateY(0); } }
   </style>
 
+  <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
   <script src="/pos/static/js/config.js"></script>

pos/templates/customers.html

@@ -2147,6 +2147,7 @@
     </div>
   </div>
 
+  <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
   <script src="/pos/static/js/customers.js"></script>

pos/templates/fleet.html

@@ -962,6 +962,7 @@
   </div>
 </div>
 
+<script src="/pos/static/js/i18n.js"></script>
 <script src="/pos/static/js/app-init.js"></script>
 <script src="/pos/static/js/sidebar.js"></script>
 <script src="/pos/static/js/fleet.js"></script>

pos/templates/inventory.html

@@ -2525,6 +2525,7 @@
     <button class="banner__dismiss" onclick="document.getElementById('offlineBanner').style.display='none'" aria-label="Cerrar">&times;</button>
   </div>
 
+  <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
   <script src="/pos/static/js/inventory.js"></script>

pos/templates/invoicing.html

@@ -2723,6 +2723,7 @@
     </div>
   </div>
 
+  <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
   <script src="/pos/static/js/invoicing.js"></script>

pos/templates/reports.html

@@ -1846,6 +1846,7 @@
   </div>
   <!-- End app-shell -->
 
+  <script src="/pos/static/js/i18n.js"></script>
   <script src="/pos/static/js/app-init.js"></script>
   <script src="/pos/static/js/sidebar.js"></script>
   <script src="/pos/static/js/reports.js"></script>

pos/templates/whatsapp.html

@@ -531,6 +531,7 @@ function posLogout(){localStorage.removeItem('pos_token');window.location.href='
 </script>
 
 <!-- Sidebar -->
+<script src="/pos/static/js/i18n.js"></script>
 <script src="/pos/static/js/whatsapp.js"></script>
 <script src="/pos/static/js/sidebar.js"></script>