Handle null values consistently and add deleted_at checks in vehiclesRoute queries

- Updated `db_object_t` to treat both `null` and string `'null'` as null values for filtering.
- Added `deleted_at IS NULL` condition in `vehiclesRoute` booking-related queries to exclude soft-deleted entries.

services/nginx/app/routes/vehiclesRoute.php

@@ -829,12 +829,14 @@ class vehiclesRoute
                     $booking = (new order_bookings_o())->getFieldsWhere([
                         'reg_1' => $reg,
                         'order_id' => null,
+                        'deleted_at' => null,
                     ], ['id', 'customer_number', 'reference', 'note']);
                     // If there is no booking with the tractor reg, check the trailer reg
                     if (!$booking) {
                         $booking = (new order_bookings_o())->getFieldsWhere([
                             'reg_2' => $reg,
                             'order_id' => null,
+                            'deleted_at' => null,
                         ], ['id', 'customer_number', 'reference', 'note']);
                     }
                     // Populate other variables
@@ -973,6 +975,7 @@ class vehiclesRoute
             [
                 'reg_1' => $search,
                 'order_id' => null,
+                'deleted_at' => null,
                 ...$filters
             ],
             ['reg_1'],
@@ -982,6 +985,7 @@ class vehiclesRoute
             [
                 'reg_2' => $search,
                 'order_id' => null,
+                'deleted_at' => null,
                 ...$filters
             ],
             ['reg_2'],