feat: H-3 출하 관리 API 구현

- ShipmentController: 출하 CRUD 및 상태 관리 API
- ShipmentService: 출하 비즈니스 로직
- Shipment, ShipmentItem 모델
- FormRequest 검증 클래스
- Swagger 문서화
- shipments, shipment_items 테이블 마이그레이션

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/Http/Requests/Shipment/ShipmentUpdateStatusRequest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Http\Requests\Shipment;
+
+use Illuminate\Foundation\Http\FormRequest;
+
+class ShipmentUpdateStatusRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    public function rules(): array
+    {
+        return [
+            'status' => 'required|in:scheduled,ready,shipping,completed',
+
+            // 상태별 추가 데이터
+            'loading_time' => 'nullable|date',
+            'loading_completed_at' => 'nullable|date',
+            'vehicle_no' => 'nullable|string|max:20',
+            'driver_name' => 'nullable|string|max:50',
+            'driver_contact' => 'nullable|string|max:50',
+            'confirmed_arrival' => 'nullable|date',
+        ];
+    }
+
+    public function messages(): array
+    {
+        return [
+            'status.required' => __('validation.required', ['attribute' => '상태']),
+            'status.in' => __('validation.in', ['attribute' => '상태']),
+        ];
+    }
+}