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

dashboard/admin.js

@@ -121,6 +121,9 @@ function showSection(sectionId) {
             case 'users':
                 loadUsers();
                 break;
+            case 'tenants':
+                loadTenants();
+                break;
         }
     }
 
@@ -2074,3 +2077,99 @@ async function toggleUserActive(userId, currentActive) {
         showAlert(e.message, 'error');
     }
 }
+
+// ─── Tenants / Modules ─────────────────────────────────────────────────────
+
+async function loadTenants() {
+    var token = localStorage.getItem('access_token');
+    var tbody = document.getElementById('tenantsTable');
+    tbody.innerHTML = '<tr><td colspan="6" class="loading"><div class="spinner"></div></td></tr>';
+
+    try {
+        var res = await fetch('/api/admin/tenants', {
+            headers: { 'Authorization': 'Bearer ' + token }
+        });
+        if (!res.ok) throw new Error('Error al cargar tenants (' + res.status + ')');
+        var data = await res.json();
+        var tenants = data.tenants || [];
+
+        if (tenants.length === 0) {
+            tbody.innerHTML = '<tr><td colspan="6" style="text-align:center; color:var(--text-secondary); padding:2rem;">No hay tenants activos</td></tr>';
+            return;
+        }
+
+        // Load modules for each tenant
+        var modulesMap = {};
+        await Promise.all(tenants.map(async function(t) {
+            try {
+                var mres = await fetch('/api/admin/tenants/' + t.id + '/modules', {
+                    headers: { 'Authorization': 'Bearer ' + token }
+                });
+                if (mres.ok) {
+                    modulesMap[t.id] = await mres.json();
+                } else {
+                    modulesMap[t.id] = {};
+                }
+            } catch (e) {
+                modulesMap[t.id] = {};
+            }
+        }));
+
+        renderTenantsTable(tenants, modulesMap);
+    } catch (e) {
+        tbody.innerHTML = '<tr><td colspan="6" style="text-align:center; color:#ef4444; padding:2rem;">' + e.message + '</td></tr>';
+    }
+}
+
+function renderTenantsTable(tenants, modulesMap) {
+    var tbody = document.getElementById('tenantsTable');
+    tbody.innerHTML = tenants.map(function(t) {
+        var mods = modulesMap[t.id] || {};
+        function toggleBtn(tenantId, key, enabled) {
+            var label = enabled ? 'Activado' : 'Desactivado';
+            var cls = enabled ? 'btn-primary' : 'btn-secondary';
+            return '<button class="btn ' + cls + '" style="font-size:0.75rem; padding:3px 10px;" ' +
+                'onclick="toggleTenantModule(' + tenantId + ', \'' + key + '\', ' + enabled + ')">' + label + '</button>';
+        }
+        return '<tr>' +
+            '<td>' + t.id + '</td>' +
+            '<td>' + (t.name || '-') + '</td>' +
+            '<td>' + toggleBtn(t.id, 'whatsapp_enabled', !!mods.whatsapp_enabled) + '</td>' +
+            '<td>' + toggleBtn(t.id, 'marketplace_enabled', !!mods.marketplace_enabled) + '</td>' +
+            '<td>' + toggleBtn(t.id, 'meli_enabled', !!mods.meli_enabled) + '</td>' +
+            '<td><button class="btn btn-primary" style="font-size:0.75rem; padding:3px 10px;" onclick="loadTenants()">🔄 Recargar</button></td>' +
+        '</tr>';
+    }).join('');
+}
+
+async function toggleTenantModule(tenantId, key, currentValue) {
+    var token = localStorage.getItem('access_token');
+    var moduleNames = {
+        'whatsapp_enabled': 'WhatsApp',
+        'marketplace_enabled': 'Marketplace',
+        'meli_enabled': 'MercadoLibre'
+    };
+    var action = currentValue ? 'desactivar' : 'activar';
+    if (!confirm('¿Seguro que deseas ' + action + ' ' + moduleNames[key] + ' para el tenant #' + tenantId + '?')) return;
+
+    try {
+        var payload = {};
+        payload[key] = !currentValue;
+        var res = await fetch('/api/admin/tenants/' + tenantId + '/modules', {
+            method: 'PUT',
+            headers: {
+                'Content-Type': 'application/json',
+                'Authorization': 'Bearer ' + token
+            },
+            body: JSON.stringify(payload)
+        });
+        if (!res.ok) {
+            var err = await res.json();
+            throw new Error(err.error || 'Error al actualizar módulo');
+        }
+        showAlert(moduleNames[key] + ' ' + (currentValue ? 'desactivado' : 'activado') + ' para tenant #' + tenantId);
+        loadTenants();
+    } catch (e) {
+        showAlert(e.message, 'error');
+    }
+}