feat: MercadoLibre integration + inventory bulk publish + WhatsApp bridge fixes

- Add MercadoLibre OAuth, listings, orders, webhooks and category search
- New marketplace_external_bp.py, meli_service.py, marketplace_external_service.py
- New marketplace_external.html/js with ML management UI
- Inventory: bulk publish to ML with category autocomplete, listing type and shipping selectors
- Inventory: new .btn--meli styles, select/label CSS fixes
- WhatsApp bridge: rate limiting, 440/515/408 error handling, stale watchdog
- DB migration v3.4_meli_integration.sql for marketplace_listings, orders, sync_queue
- Add Celery tasks for ML sync and webhook processing
- Sidebar: MercadoLibre navigation link

pos/static/js/config.js

@@ -19,6 +19,11 @@ const Config = (() => {
         return true;
     }
 
+    function escapeHtml(text) {
+        if (!text) return '';
+        return String(text).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
+    }
+
     function headers() {
         return { 'Authorization': `Bearer ${token()}`, 'Content-Type': 'application/json' };
     }
@@ -623,6 +628,67 @@ const Config = (() => {
         }
     }
 
+    // -------------------------------------------------------------------------
+    // Allowed Part Brands
+    // -------------------------------------------------------------------------
+    async function loadAllowedBrands() {
+        var container = document.getElementById('allowed-brands-container');
+        if (!container) return;
+        try {
+            var res = await fetch(API + '/available-brands', { headers: headers() });
+            if (!res.ok) throw new Error('Failed to load brands');
+            var d = await res.json();
+            var allBrands = d.brands || [];
+
+            var res2 = await fetch(API + '/allowed-brands', { headers: headers() });
+            if (!res2.ok) throw new Error('Failed to load allowed brands');
+            var d2 = await res2.json();
+            var allowed = d2.brands || [];
+
+            if (!allBrands.length) {
+                container.innerHTML = '<p style="color:var(--color-text-muted);font-size:var(--text-body-sm);">No hay marcas disponibles.</p>';
+                return;
+            }
+
+            var html = '';
+            allBrands.forEach(function(b) {
+                var checked = allowed.indexOf(b) !== -1 ? 'checked' : '';
+                html += '<label style="display:flex;align-items:center;gap:var(--space-2);cursor:pointer;font-size:var(--text-body-sm);color:var(--color-text-primary);padding:var(--space-1);">' +
+                    '<input type="checkbox" value="' + escapeHtml(b) + '" data-brand-checkbox ' + checked + ' style="width:16px;height:16px;cursor:pointer;">' +
+                    escapeHtml(b) + '</label>';
+            });
+            container.innerHTML = html;
+        } catch (e) {
+            console.error('Config.loadAllowedBrands:', e);
+            if (container) container.innerHTML = '<p style="color:var(--color-error);font-size:var(--text-body-sm);">Error al cargar marcas.</p>';
+        }
+    }
+
+    async function saveAllowedBrands() {
+        var btn = document.getElementById('btn-save-allowed-brands');
+        if (btn) { btn.disabled = true; btn.textContent = 'Guardando...'; }
+        try {
+            var checked = [];
+            document.querySelectorAll('[data-brand-checkbox]').forEach(function(cb) {
+                if (cb.checked) checked.push(cb.value);
+            });
+            var res = await fetch(API + '/allowed-brands', {
+                method: 'PUT',
+                headers: headers(),
+                body: JSON.stringify({ brands: checked })
+            });
+            if (!res.ok) {
+                var err = await res.json().catch(function() { return { error: res.statusText }; });
+                throw new Error(err.error || 'Save failed');
+            }
+            toast('Marcas permitidas actualizadas');
+        } catch (e) {
+            toast(e.message, 'error');
+        } finally {
+            if (btn) { btn.disabled = false; btn.textContent = 'Guardar Marcas'; }
+        }
+    }
+
     // -------------------------------------------------------------------------
     // Init
     // -------------------------------------------------------------------------
@@ -650,6 +716,12 @@ const Config = (() => {
             btnCompat.addEventListener('click', saveVehicleCompatSource);
         }
 
+        // Allowed brands save button
+        var btnBrands = document.getElementById('btn-save-allowed-brands');
+        if (btnBrands) {
+            btnBrands.addEventListener('click', saveAllowedBrands);
+        }
+
         // Kiosk mode toggle
         var kioskToggle = document.getElementById('cfg-kiosk-mode');
         if (kioskToggle && window.NexusKiosk) {
@@ -671,12 +743,13 @@ const Config = (() => {
         loadBusiness();
         loadCurrency();
         loadVehicleCompatSource();
+        loadAllowedBrands();
     }
 
     document.addEventListener('DOMContentLoaded', init);
 
     return {
-        init, setTheme, selectThemeOption,
+        init, setTheme, selectThemeOption, loadAllowedBrands, saveAllowedBrands,
         loadBranches, loadEmployees, saveBranch, saveEmployee, editEmployee,
         loadBusiness, saveBusiness, saveTaxParams,
         loadCurrency, saveCurrency,