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_learning.py

@@ -0,0 +1,127 @@
+"""
+WhatsApp Learning Service — ruta de aprendizaje para piezas no resueltas.
+
+Registra sesiones donde el bot no pudo identificar una pieza, y las resuelve
+asíncronamente cuando el cliente realiza una compra futura.
+"""
+
+import json
+
+
+def register_unresolved_search(phone, customer_id, description, offered_parts, tenant_conn):
+    """Registrar una sesión no resuelta para aprendizaje futuro."""
+    if not tenant_conn or not phone or not description:
+        return None
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        INSERT INTO wa_learning_sessions (phone, customer_id, description, offered_parts, status, created_at)
+        VALUES (%s, %s, %s, %s, 'pending', NOW())
+        RETURNING id
+    """, (phone, customer_id, description, json.dumps(offered_parts or [])))
+    sid = cur.fetchone()[0]
+    tenant_conn.commit()
+    cur.close()
+    return sid
+
+
+def find_pending_sessions(phone, tenant_conn):
+    """Buscar sesiones pendientes de aprendizaje para un número WA."""
+    if not tenant_conn or not phone:
+        return []
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        SELECT id, description, offered_parts, created_at
+        FROM wa_learning_sessions
+        WHERE phone = %s AND status = 'pending'
+        ORDER BY created_at DESC
+    """, (phone,))
+    rows = cur.fetchall()
+    cur.close()
+    return [{'id': r[0], 'description': r[1], 'offered_parts': r[2], 'created_at': str(r[3])} for r in rows]
+
+
+def find_pending_sessions_by_customer(customer_id, tenant_conn):
+    """Buscar sesiones pendientes por customer_id."""
+    if not tenant_conn or not customer_id:
+        return []
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        SELECT id, phone, description, offered_parts, created_at
+        FROM wa_learning_sessions
+        WHERE customer_id = %s AND status = 'pending'
+        ORDER BY created_at DESC
+    """, (customer_id,))
+    rows = cur.fetchall()
+    cur.close()
+    return [{'id': r[0], 'phone': r[1], 'description': r[2], 'offered_parts': r[3], 'created_at': str(r[4])} for r in rows]
+
+
+def resolve_session(session_id, resolved_part_id, sale_id, tenant_conn):
+    """Marcar sesión como resuelta con la pieza comprada."""
+    if not tenant_conn or not session_id:
+        return
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        UPDATE wa_learning_sessions
+        SET status = 'learned', resolved_part_id = %s, resolution_sale_id = %s, resolved_at = NOW()
+        WHERE id = %s
+    """, (resolved_part_id, sale_id, session_id))
+    tenant_conn.commit()
+    cur.close()
+
+
+def get_learning_pairs_for_training(tenant_conn, limit=100):
+    """Obtener pares (descripción del cliente → pieza real) para entrenamiento."""
+    if not tenant_conn:
+        return []
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        SELECT l.description, i.name, i.part_number, i.brand
+        FROM wa_learning_sessions l
+        JOIN inventory i ON i.id = l.resolved_part_id
+        WHERE l.status = 'learned' AND l.resolved_at > NOW() - INTERVAL '90 days'
+        ORDER BY l.resolved_at DESC
+        LIMIT %s
+    """, (limit,))
+    rows = cur.fetchall()
+    cur.close()
+    return [{'description': r[0], 'part_name': r[1], 'part_number': r[2], 'brand': r[3]} for r in rows]
+
+
+def check_learning_resolution(sale_id, customer_id, tenant_conn):
+    """
+    Hook para llamar después de completar una venta.
+    Verifica si esta venta resuelve una sesión de aprendizaje pendiente.
+    """
+    if not tenant_conn or not customer_id:
+        return
+
+    sessions = find_pending_sessions_by_customer(customer_id, tenant_conn)
+    if not sessions:
+        return
+
+    # Obtener items de esta venta
+    cur = tenant_conn.cursor()
+    cur.execute("""
+        SELECT si.inventory_id, i.name, i.part_number
+        FROM sale_items si
+        JOIN inventory i ON i.id = si.inventory_id
+        WHERE si.sale_id = %s
+    """, (sale_id,))
+    sale_items = cur.fetchall()
+    cur.close()
+
+    if not sale_items:
+        return
+
+    # Matching heurístico
+    for sess in sessions:
+        desc_words = set(sess['description'].lower().split())
+        for inv_id, item_name, part_number in sale_items:
+            item_words = set(item_name.lower().split())
+            # Intersección de palabras significativas
+            common = desc_words & item_words - {'de', 'la', 'el', 'para', 'un', 'una', 'con', 'y', 'o', 'en', 'al', 'del', 'los', 'las'}
+            if len(common) >= 2:
+                resolve_session(sess['id'], inv_id, sale_id, tenant_conn)
+                print(f"[WA-LEARN] Resolved session {sess['id']} with sale {sale_id}, item {inv_id}")
+                break