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

pos/static/js/config.js

@@ -689,6 +689,53 @@ const Config = (() => {
         }
     }
 
+    // -------------------------------------------------------------------------
+    // Modules / Integrations
+    // -------------------------------------------------------------------------
+    async function loadModules() {
+        try {
+            var res = await fetch(API + '/modules', { headers: headers() });
+            if (!res.ok) return;
+            var data = await res.json();
+            var cbWa = document.getElementById('cfg-module-whatsapp');
+            var cbMp = document.getElementById('cfg-module-marketplace');
+            var cbMeli = document.getElementById('cfg-module-meli');
+            if (cbWa) cbWa.checked = data.whatsapp !== false;
+            if (cbMp) cbMp.checked = data.marketplace !== false;
+            if (cbMeli) cbMeli.checked = data.meli !== false;
+            localStorage.setItem('pos_modules', JSON.stringify(data));
+        } catch (e) {
+            console.error('Config.loadModules:', e);
+        }
+    }
+
+    async function saveModules() {
+        var btn = event.target;
+        if (btn) { btn.disabled = true; btn.textContent = 'Guardando...'; }
+        try {
+            var data = {
+                whatsapp: document.getElementById('cfg-module-whatsapp').checked,
+                marketplace: document.getElementById('cfg-module-marketplace').checked,
+                meli: document.getElementById('cfg-module-meli').checked,
+            };
+            var res = await fetch(API + '/modules', {
+                method: 'PUT',
+                headers: headers(),
+                body: JSON.stringify(data)
+            });
+            if (!res.ok) {
+                var err = await res.json().catch(function() { return { error: res.statusText }; });
+                throw new Error(err.error || 'Save failed');
+            }
+            localStorage.setItem('pos_modules', JSON.stringify(data));
+            toast('Módulos actualizados');
+        } catch (e) {
+            toast(e.message, 'error');
+        } finally {
+            if (btn) { btn.disabled = false; btn.textContent = 'Guardar módulos'; }
+        }
+    }
+
     // -------------------------------------------------------------------------
     // Init
     // -------------------------------------------------------------------------
@@ -744,6 +791,7 @@ const Config = (() => {
         loadCurrency();
         loadVehicleCompatSource();
         loadAllowedBrands();
+        loadModules();
     }
 
     document.addEventListener('DOMContentLoaded', init);
@@ -753,6 +801,7 @@ const Config = (() => {
         loadBranches, loadEmployees, saveBranch, saveEmployee, editEmployee,
         loadBusiness, saveBusiness, saveTaxParams,
         loadCurrency, saveCurrency,
+        loadModules, saveModules,
         openModal, closeModal
     };
     // Register Cmd+K items