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/src/Exceptions/InvalidVehicleSelectionException.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Modules\Booking\Exceptions;
+
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+use Modules\Shared\Enums\VehicleOption;
+use RuntimeException;
+
+class InvalidVehicleSelectionException extends RuntimeException
+{
+    public static function frontSeatLimitExceeded(int $requested, int $max): self
+    {
+        return new self("Front seat request [{$requested}] exceeds the max of [{$max}] per booking.");
+    }
+
+    public static function optionDisabled(VehicleOption $vehicleOption): self
+    {
+        return new self("Vehicle option [{$vehicleOption->value}] is not currently available for booking.");
+    }
+
+    public static function duplicateOption(VehicleOption $vehicleOption): self
+    {
+        return new self("Vehicle option [{$vehicleOption->value}] was selected more than once — combine it into a single selection.");
+    }
+
+    public static function wholeVehicleCannotBeCombined(): self
+    {
+        return new self('Whole Vehicle cannot be combined with other vehicle options in the same booking.');
+    }
+
+    /**
+     * A rejected vehicle selection is a client input problem, not a server
+     * error — surface it as 422 rather than the default 500. A broader JSON
+     * error envelope for all of api/* is Phase 6 (T6.3); this keeps the
+     * mapping local until that lands.
+     */
+    public function render(Request $request): ?JsonResponse
+    {
+        if ($request->expectsJson()) {
+            return response()->json(['message' => $this->getMessage()], 422);
+        }
+
+        return null;
+    }
+}