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/server.py

@@ -16,6 +16,7 @@ sys.path.insert(0, os.path.join(_base, '..', 'pos'))   # pos/ for auth, services
 sys.path.insert(0, os.path.join(_base, '..'))           # root config.py (has DB_URL)
 from config import DB_URL
 from auth import hash_password, check_password, create_access_token, create_refresh_token, decode_token, require_auth
+from tenant_db import get_tenant_conn
 from services.translations import translate_part_name, translate_category
 
 sys.path.insert(0, os.path.join(_base, '..', 'pos'))
@@ -4628,6 +4629,76 @@ def part_aftermarket(part_id):
         session.close()
 
 
+# ============================================================================
+# Tenant Module Config Endpoints
+# ============================================================================
+
+MODULE_CONFIG_KEYS = [
+    'whatsapp_enabled',
+    'marketplace_enabled',
+    'meli_enabled',
+]
+
+
+@app.route('/api/admin/tenants')
+def api_admin_tenants():
+    session = Session()
+    try:
+        rows = session.execute(text(
+            "SELECT id, name, db_name, is_active, is_seller FROM tenants WHERE is_active = true ORDER BY id"
+        )).mappings().all()
+        return jsonify({'tenants': [dict(r) for r in rows]})
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+    finally:
+        session.close()
+
+
+@app.route('/api/admin/tenants/<int:tenant_id>/modules')
+def api_admin_tenant_modules(tenant_id):
+    try:
+        conn = get_tenant_conn(tenant_id)
+        cur = conn.cursor()
+        result = {}
+        for key in MODULE_CONFIG_KEYS:
+            cur.execute("SELECT value FROM tenant_config WHERE key = %s", (key,))
+            row = cur.fetchone()
+            result[key] = (row[0] or '').lower() == 'true' if row else False
+        cur.close()
+        conn.close()
+        return jsonify(result)
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+
+
+@app.route('/api/admin/tenants/<int:tenant_id>/modules', methods=['PUT'])
+def api_admin_tenant_modules_update(tenant_id):
+    data = request.get_json() or {}
+    if not data:
+        return jsonify({'error': 'No data provided'}), 400
+
+    try:
+        conn = get_tenant_conn(tenant_id)
+        cur = conn.cursor()
+        for key, value in data.items():
+            if key not in MODULE_CONFIG_KEYS:
+                continue
+            cur.execute(
+                """
+                INSERT INTO tenant_config (key, value, updated_at)
+                VALUES (%s, %s, NOW())
+                ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value, updated_at = NOW()
+                """,
+                (key, 'true' if value else 'false'),
+            )
+        conn.commit()
+        cur.close()
+        conn.close()
+        return jsonify({'ok': True})
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+
+
 # ============================================================================
 # Static files from dashboard root (CSS/JS/HTML)
 # ============================================================================