Remove legacy booking completion forms and related logic

- Deleted `complete_booking_f` and `generate_booking_wash_certificate_f` classes.
- Updated tests to ensure legacy booking completion routes are disabled.
- Introduced tests for POST `/order-bookings/complete` to enforce POS-based booking completion management.
- Added `/collected-invoices/split-by-month` route with API and unit tests for splitting collections into monthly periods.
- Refactored impacted files to exclude legacy references and ensure continued compatibility with POS processes.

services/nginx/app/classes/form.php

@@ -12,8 +12,6 @@ use Exception;
 use forms\form_helper_c;
 use forms\objects\book_interior_wash_f;
 use forms\objects\book_wash_f;
-use forms\objects\complete_booking_f;
-use forms\objects\generate_booking_wash_certificate_f;
 use objects\form_submissions_o;
 use traits\form_t;
 
@@ -30,25 +28,12 @@ class form
      * @var book_wash_f $book_wash The BOOK_WASH form
      */
     public book_wash_f $book_wash;
-    /**
-     * The GENERATE_BOOKING_CERTIFICATE form
-     * @var generate_booking_wash_certificate_f $generate_booking_wash_certificate The GENERATE_BOOKING_CERTIFICATE form
-     */
-    public generate_booking_wash_certificate_f $generate_booking_wash_certificate;
-
-    /**
-     * The COMPLETE_BOOKING_WITHOUT_WASH_CERTIFICATE form
-     * @var complete_booking_f $complete_booking_without_wash_certificate The COMPLETE_BOOKING_WITHOUT_WASH_CERTIFICATE form
-     */
-    public complete_booking_f $complete_booking_without_wash_certificate;
     public $last_submitted_form;
     public form_submissions_o $form_submission;
 
     public function __construct()
     {
         $this->book_wash = new book_wash_f();
-        $this->generate_booking_wash_certificate = new generate_booking_wash_certificate_f();
-        $this->complete_booking_without_wash_certificate = new complete_booking_f();
     }
 
     /**
@@ -109,4 +94,4 @@ class form
         }
         throw new Exception('The form was not found');
     }
-}
+}