feat: [shipment] 배차정보 다중 행 시스템 — shipment_vehicle_dispatches 테이블 추가

- 신규 마이그레이션: shipment_vehicle_dispatches 테이블 (seq, logistics_company, arrival_datetime, tonnage, vehicle_no, driver_contact, remarks)
- 신규 모델: ShipmentVehicleDispatch (ShipmentItem 패턴 복제)
- Shipment 모델: vehicleDispatches() HasMany 관계 추가
- ShipmentService: syncDispatches() 추가, store/update/delete/show/index에서 연동
- FormRequest: Store/Update에 vehicle_dispatches 배열 검증 규칙 추가
- delivery_method 검증에 확장 옵션 추가

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Http/Requests/Shipment/ShipmentUpdateRequest.php

@@ -19,7 +19,7 @@ public function rules(): array
             'order_id' => 'nullable|integer|exists:orders,id',
             'scheduled_date' => 'nullable|date',
             'priority' => 'nullable|in:urgent,normal,low',
-            'delivery_method' => 'nullable|in:pickup,direct,logistics',
+            'delivery_method' => 'nullable|in:pickup,direct,logistics,direct_dispatch,loading,kyungdong_delivery,daesin_delivery,kyungdong_freight,daesin_freight,self_pickup',
 
             // 발주처/배송 정보
             'client_id' => 'nullable|integer|exists:clients,id',
@@ -53,6 +53,16 @@ public function rules(): array
             // 기타
             'remarks' => 'nullable|string',
 
+            // 배차정보
+            'vehicle_dispatches' => 'nullable|array',
+            'vehicle_dispatches.*.seq' => 'nullable|integer|min:1',
+            'vehicle_dispatches.*.logistics_company' => 'nullable|string|max:100',
+            'vehicle_dispatches.*.arrival_datetime' => 'nullable|date',
+            'vehicle_dispatches.*.tonnage' => 'nullable|string|max:20',
+            'vehicle_dispatches.*.vehicle_no' => 'nullable|string|max:20',
+            'vehicle_dispatches.*.driver_contact' => 'nullable|string|max:50',
+            'vehicle_dispatches.*.remarks' => 'nullable|string',
+
             // 출하 품목
             'items' => 'nullable|array',
             'items.*.seq' => 'nullable|integer|min:1',