feat: module toggles in POS config and Instance Manager

- Add GET/PUT /pos/api/config/modules endpoints in POS config_bp.py
- Update sidebar.js to filter nav items based on enabled modules
- Add Modules section to POS config.html with toggles for WhatsApp, Marketplace, MercadoLibre
- Add module load/save logic to POS config.js
- Preload modules in app-init.js for sidebar caching

- Add tenant module management to Instance Manager
  - get_tenant_modules / update_tenant_modules in tenant_service.py
  - GET/PUT /api/tenants/<id>/modules endpoints in tenants_bp.py
  - Add modules modal to manager index.html
  - Add module editing UI and logic to manager.js
  - Add toggle-switch CSS to manager.css

manager/static/css/manager.css

@@ -661,3 +661,42 @@ body {
     .sidebar-brand span, .nav-item span, .user-info span { display: none; }
     .stats-grid { grid-template-columns: 1fr; }
 }
+
+/* Toggle switch for modules modal */
+.toggle-switch {
+    position: relative;
+    display: inline-block;
+    width: 44px;
+    height: 24px;
+    cursor: pointer;
+}
+.toggle-switch input {
+    opacity: 0;
+    width: 0;
+    height: 0;
+}
+.toggle-slider {
+    position: absolute;
+    inset: 0;
+    background: var(--border);
+    border-radius: 24px;
+    transition: background 0.2s;
+}
+.toggle-slider::before {
+    content: "";
+    position: absolute;
+    height: 18px;
+    width: 18px;
+    left: 3px;
+    bottom: 3px;
+    background: white;
+    border-radius: 50%;
+    transition: transform 0.2s;
+    box-shadow: 0 1px 3px rgba(0,0,0,0.2);
+}
+.toggle-switch input:checked + .toggle-slider {
+    background: var(--success);
+}
+.toggle-switch input:checked + .toggle-slider::before {
+    transform: translateX(20px);
+}