Add Booking module: model, create/read/cancel API, Filament resource (T4.1-T4.7)

- Booking model with booking_vehicle_options line items (supports mixing
  vehicle options like front_seat + back_seat in one booking), price
  snapshot, status machine, and driver/car assignment fields
- BookingService: front-seat max, disabled-option toggles, duplicate-option
  and whole-vehicle-exclusivity guards
- CreateBookingAction, CancelBookingAction, AssignDriverAction
- BookingRefGenerator: sequential EVB-AAAAA1-style refs via row lock
- POST/GET/cancel booking API endpoints (Sanctum, ownership + admin policy)
- BookingPlugin + Filament BookingResource: list, detail view, Cancel and
  Assign Driver actions (shared between table and detail page)
- domain.md updated for multi-vehicle-option bookings (§2) and driver/
  vehicle assignment (§5a)

app-modules/booking/tests/Unit/BookingRefGeneratorTest.php

@@ -0,0 +1,40 @@
+<?php
+
+use Modules\Booking\Models\Booking;
+use Modules\Booking\Services\BookingRefGenerator;
+
+test('the first booking ref starts the sequence at AAAAA1', function () {
+    $ref = (new BookingRefGenerator)->generate();
+
+    expect($ref)->toBe('EVB-AAAAA1');
+});
+
+test('the ref increments digit by digit through the alphabet', function () {
+    Booking::factory()->create(['booking_ref' => 'EVB-AAAAA9']);
+
+    expect((new BookingRefGenerator)->generate())->toBe('EVB-AAAAAA');
+});
+
+test('the ref carries over into the next position once the alphabet is exhausted', function () {
+    Booking::factory()->create(['booking_ref' => 'EVB-AAAAZZ']);
+
+    expect((new BookingRefGenerator)->generate())->toBe('EVB-AAAB11');
+});
+
+test('generated refs are unique across repeated calls', function () {
+    $refs = [];
+
+    for ($i = 0; $i < 20; $i++) {
+        $ref = (new BookingRefGenerator)->generate();
+        Booking::factory()->create(['booking_ref' => $ref]);
+        $refs[] = $ref;
+    }
+
+    expect($refs)->toEqual(array_unique($refs));
+});
+
+test('an unrecognised existing ref format resets the sequence rather than throwing', function () {
+    Booking::factory()->create(['booking_ref' => 'LEGACY-2024-0001']);
+
+    expect((new BookingRefGenerator)->generate())->toBe('EVB-AAAAA1');
+});