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/services/wa_customer.py

@@ -0,0 +1,140 @@
+"""
+WhatsApp Customer Service — identificación y vinculación de clientes.
+
+Funciones para buscar, crear y vincular clientes desde el flujo de WhatsApp.
+"""
+
+import re
+
+
+def find_customer_by_phone(phone, tenant_conn):
+    """Buscar cliente por número de teléfono exacto o parcial."""
+    if not tenant_conn or not phone:
+        return []
+    cur = tenant_conn.cursor()
+    # Limpiar phone de prefijos internacionales para búsqueda flexible
+    clean = phone.replace('+52', '').replace('52', '').lstrip('1')
+    cur.execute("""
+        SELECT id, name, phone, address, rfc
+        FROM customers
+        WHERE phone = %s OR phone LIKE %s OR phone LIKE %s
+        LIMIT 5
+    """, (phone, f'%{clean}', f'%{clean[-10:]}' if len(clean) >= 10 else f'%{clean}'))
+    rows = cur.fetchall()
+    cur.close()
+    return [{'id': r[0], 'name': r[1], 'phone': r[2], 'address': r[3], 'rfc': r[4]} for r in rows]
+
+
+def find_customer_by_name(name, tenant_conn):
+    """Buscar cliente por nombre (ILIKE)."""
+    if not tenant_conn or not name:
+        return []
+    cur = tenant_conn.cursor()
+    # Buscar por nombre completo o primer palabra
+    first_word = name.split()[0] if name else name
+    cur.execute("""
+        SELECT id, name, phone, address, rfc
+        FROM customers
+        WHERE name ILIKE %s OR name ILIKE %s
+        LIMIT 5
+    """, (f'%{name}%', f'%{first_word}%'))
+    rows = cur.fetchall()
+    cur.close()
+    return [{'id': r[0], 'name': r[1], 'phone': r[2], 'address': r[3], 'rfc': r[4]} for r in rows]
+
+
+def search_customers(query, tenant_conn):
+    """Buscar por teléfono o nombre."""
+    if not tenant_conn or not query:
+        return []
+    # Detectar si es número de teléfono
+    digits = re.sub(r'\D', '', query)
+    if len(digits) >= 7:
+        by_phone = find_customer_by_phone(digits, tenant_conn)
+        if by_phone:
+            return by_phone
+    return find_customer_by_name(query, tenant_conn)
+
+
+def get_customer_by_id(tenant_conn, customer_id):
+    """Obtener cliente por ID."""
+    if not tenant_conn or not customer_id:
+        return None
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        SELECT id, name, phone, address, rfc, vehicle_info
+        FROM customers WHERE id = %s
+    """, (customer_id,))
+    row = cur.fetchone()
+    cur.close()
+    if row:
+        return {
+            'id': row[0], 'name': row[1], 'phone': row[2],
+            'address': row[3], 'rfc': row[4], 'vehicle_info': row[5]
+        }
+    return None
+
+
+def create_customer(tenant_conn, phone, name, email=None, address=None, rfc=None):
+    """Crear cliente nuevo desde WhatsApp."""
+    if not tenant_conn:
+        return None
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        INSERT INTO customers (name, phone, email, address, rfc, is_active, created_at)
+        VALUES (%s, %s, %s, %s, %s, TRUE, NOW())
+        RETURNING id
+    """, (name, phone, email, address, rfc))
+    cid = cur.fetchone()[0]
+    tenant_conn.commit()
+    cur.close()
+    return cid
+
+
+def link_wa_customer(phone, customer_id, tenant_conn):
+    """Vincular número WA a cliente permanentemente."""
+    if not tenant_conn or not phone or not customer_id:
+        return
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        INSERT INTO wa_customer_links (phone, customer_id, updated_at)
+        VALUES (%s, %s, NOW())
+        ON CONFLICT (phone) DO UPDATE SET customer_id = EXCLUDED.customer_id, updated_at = NOW()
+    """, (phone, customer_id))
+    tenant_conn.commit()
+    cur.close()
+
+
+def get_linked_customer(phone, tenant_conn):
+    """Obtener customer_id vinculado a un número WA."""
+    if not tenant_conn or not phone:
+        return None
+    cur = tenant_conn.cursor()
+    cur.execute("SELECT customer_id FROM wa_customer_links WHERE phone = %s", (phone,))
+    row = cur.fetchone()
+    cur.close()
+    return row[0] if row else None
+
+
+def get_customer_address(tenant_conn, customer_id):
+    """Obtener dirección del cliente."""
+    if not tenant_conn or not customer_id:
+        return None
+    cur = tenant_conn.cursor()
+    cur.execute("SELECT address FROM customers WHERE id = %s", (customer_id,))
+    row = cur.fetchone()
+    cur.close()
+    return row[0] if row and row[0] else None
+
+
+def update_customer_address(tenant_conn, customer_id, address):
+    """Actualizar dirección del cliente."""
+    if not tenant_conn or not customer_id or not address:
+        return
+    cur = tenant_conn.cursor()
+    cur.execute(
+        "UPDATE customers SET address = %s WHERE id = %s",
+        (address, customer_id)
+    )
+    tenant_conn.commit()
+    cur.close()