feat(workshop): vehicles must be assigned to a customer

- Added customer_id column to fleet_vehicles with FK to customers.

- Enforced customer_id on create_vehicle endpoints (workshop and fleet).

- New vehicle modal now requires a selected customer and stores customer_id.

- Migration v4.13 applied to all tenants.

pos/blueprints/service_order_bp.py

@@ -413,25 +413,36 @@ def create_customer_for_workshop():
 @service_order_bp.route('/vehicles', methods=['POST'])
 @require_auth('workshop.edit')
 def create_vehicle_for_workshop():
-    """Create a fleet vehicle directly from the workshop flow."""
+    """Create a fleet vehicle directly from the workshop flow.
+
+    Vehicles must be assigned to a customer.
+    """
     data = request.get_json() or {}
     if not data.get('plate') and not data.get('vin'):
         return jsonify({'error': 'Se requiere placa o VIN'}), 400
+    if not data.get('customer_id'):
+        return jsonify({'error': 'El vehiculo debe estar asignado a un cliente'}), 400
 
     conn = get_tenant_conn(g.tenant_id)
     cur = conn.cursor()
     try:
+        cur.execute("SELECT name FROM customers WHERE id = %s", (data['customer_id'],))
+        cust = cur.fetchone()
+        if not cust:
+            cur.close(); conn.close()
+            return jsonify({'error': 'Cliente no encontrado'}), 404
+
         cur.execute("""
             INSERT INTO fleet_vehicles
-                (branch_id, plate, vin, make, model, year,
+                (branch_id, customer_id, plate, vin, make, model, year,
                  current_mileage, fuel_type, color, owner_name, notes)
-            VALUES (%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s)
+            VALUES (%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s)
             RETURNING id
         """, (
-            data.get('branch_id', g.branch_id), data.get('plate'), data.get('vin'),
+            data.get('branch_id', g.branch_id), data['customer_id'], data.get('plate'), data.get('vin'),
             data.get('make'), data.get('model'), data.get('year'),
             data.get('current_mileage', 0), data.get('fuel_type', 'gasolina'),
-            data.get('color'), data.get('owner_name'), data.get('notes'),
+            data.get('color'), cust[0], data.get('notes'),
         ))
         vehicle_id = cur.fetchone()[0]
         conn.commit()