feat: Fase 1-3 completas - precios proveedor, multi-sucursal, factura global

Fase 1: Lista de precios de proveedor
- Tabla supplier_catalog_prices en master DB
- Endpoints GET/POST/PUT/DELETE /supplier-catalog/prices
- Upload CSV/Excel de precios de proveedor
- Visualizacion de supplier_price en catalogo y POS

Fase 2: Multi-sucursal completo
- Migracion v4.0: inventory.branch_id=NULL, tabla inventory_stock
- Campos fiscales en branches (RFC, regimen, CP, serie CFDI, certificados)
- Trigger trg_update_inventory_stock para sincronizar stock por sucursal
- Backend config_bp.py con CRUD de sucursales fiscales
- Backend inventory_bp.py y pos_bp.py refactorizados para inventario compartido
- Backend invoicing_bp.py usa datos fiscales de la sucursal de la venta
- Frontend config.html/js con modal de sucursales expandido

Fase 3: Factura global mensual
- Migracion v4.1: tablas global_invoice_sales, sales.global_invoiced_at
- build_global_invoice_xml() con InformacionGlobal SAT-compliant
- Servicio global_invoice.py para agrupar ventas PUE <=000
- Endpoints POST/GET /global-invoice y /global-invoice/eligible-sales
- Frontend invoicing.html/js con boton y modal de factura global

pos/static/js/invoicing.js

@@ -478,6 +478,51 @@ const Invoicing = (() => {
         alert('Nota de credito: proximamente');
     }
 
+    // ---- Global Invoice ----
+    function openGlobalInvoiceModal() {
+        const now = new Date();
+        document.getElementById('global-year').value = now.getFullYear();
+        document.getElementById('global-month').value = now.getMonth() + 1;
+        document.getElementById('global-preview').innerHTML = 'Presiona "Vista previa" para ver ventas elegibles.';
+        document.getElementById('modalGlobalInvoice').style.display = 'flex';
+    }
+
+    async function previewGlobalInvoice() {
+        const year = document.getElementById('global-year').value;
+        const month = document.getElementById('global-month').value;
+        const preview = document.getElementById('global-preview');
+        preview.innerHTML = 'Cargando...';
+        try {
+            const res = await api(`/global-invoice/eligible-sales?year=${year}&month=${month}`);
+            preview.innerHTML = `<strong>${res.count} ventas elegibles</strong> — Total: $${fmt(res.total)}<br><small>${res.sales.map(s => '#' + s.id).join(', ')}</small>`;
+        } catch (e) {
+            preview.innerHTML = '<span style="color:var(--color-error);">Error: ' + e.message + '</span>';
+        }
+    }
+
+    async function generateGlobalInvoice() {
+        const year = parseInt(document.getElementById('global-year').value, 10);
+        const month = parseInt(document.getElementById('global-month').value, 10);
+        const btn = document.querySelector('#modalGlobalInvoice .btn--primary');
+        const originalText = btn.textContent;
+        btn.disabled = true;
+        btn.textContent = 'Generando...';
+        try {
+            const res = await api('/global-invoice', {
+                method: 'POST',
+                body: JSON.stringify({ year, month })
+            });
+            alert(`Factura global generada: ${res.provisional_folio} (${res.sales_count} ventas, $${fmt(res.total)})`);
+            document.getElementById('modalGlobalInvoice').style.display = 'none';
+            loadFacturas();
+        } catch (e) {
+            alert('Error: ' + e.message);
+        } finally {
+            btn.disabled = false;
+            btn.textContent = originalText;
+        }
+    }
+
     // Expose switchTab globally for onclick handlers in HTML
     window.switchTab = switchTab;
     window.showNewInvoiceModal = showNewInvoiceModal;
@@ -489,6 +534,7 @@ const Invoicing = (() => {
         switchTab, loadFacturas, loadNotas, loadComplementos, loadCancelaciones,
         showDetail, showCancelModal, confirmCancel, processQueue,
         showNewInvoiceModal, closeNewInvoiceModal, submitNewInvoice, notaCreditoPlaceholder,
+        openGlobalInvoiceModal, previewGlobalInvoice, generateGlobalInvoice,
     };
     // Register Cmd+K items
     if (typeof registerCmdKItem === "function") {