feat: 수주관리(Order Management) API Phase 1.1 구현

- OrderService 구현 (index, stats, show, store, update, destroy, updateStatus)
- OrderController 구현 (7개 API 엔드포인트)
- FormRequest 클래스 3개 생성 (Store, Update, UpdateStatus)
- 상태 전환 규칙 검증 (DRAFT → CONFIRMED → IN_PROGRESS → COMPLETED/CANCELLED)
- 수주번호 자동 생성 (ORD{YYYYMMDD}{0001} 형식)
- Swagger API 문서 작성 (OrderApi.php)
- i18n 메시지 키 추가 (ko/en)

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

lang/en/message.php

@@ -93,4 +93,13 @@
         'deleted' => 'File has been deleted.',
         'fetched' => 'File list retrieved successfully.',
     ],
+
+    // Order Management
+    'order' => [
+        'fetched' => 'Order retrieved successfully.',
+        'created' => 'Order has been created.',
+        'updated' => 'Order has been updated.',
+        'deleted' => 'Order has been deleted.',
+        'status_updated' => 'Order status has been updated.',
+    ],
 ];