feat: 장비 관리 API 연동 구현

- Equipment 관련 DTO 모델 생성 (Request/Response/List/History/In/Out/IO)
- EquipmentRemoteDataSource 구현 (10개 API 엔드포인트)
- EquipmentService 비즈니스 로직 구현
- Controller를 ChangeNotifier 패턴으로 개선
- 장비 목록 화면에 Provider 패턴 및 무한 스크롤 적용
- 장비 입고 화면 API 연동 및 비동기 처리
- DI 컨테이너에 Equipment 관련 의존성 등록
- API/Mock 데이터 소스 전환 가능 (Feature Flag)
- API 통합 진행 상황 문서 업데이트

lib/data/models/equipment/equipment_request.dart

@@ -0,0 +1,48 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'equipment_request.freezed.dart';
+part 'equipment_request.g.dart';
+
+@freezed
+class CreateEquipmentRequest with _$CreateEquipmentRequest {
+  const factory CreateEquipmentRequest({
+    required String equipmentNumber,
+    String? category1,
+    String? category2,
+    String? category3,
+    required String manufacturer,
+    String? modelName,
+    String? serialNumber,
+    DateTime? purchaseDate,
+    double? purchasePrice,
+    String? remark,
+  }) = _CreateEquipmentRequest;
+
+  factory CreateEquipmentRequest.fromJson(Map<String, dynamic> json) =>
+      _$CreateEquipmentRequestFromJson(json);
+}
+
+@freezed
+class UpdateEquipmentRequest with _$UpdateEquipmentRequest {
+  const factory UpdateEquipmentRequest({
+    String? category1,
+    String? category2,
+    String? category3,
+    String? manufacturer,
+    String? modelName,
+    String? serialNumber,
+    String? barcode,
+    DateTime? purchaseDate,
+    double? purchasePrice,
+    String? status,
+    int? currentCompanyId,
+    int? currentBranchId,
+    int? warehouseLocationId,
+    DateTime? lastInspectionDate,
+    DateTime? nextInspectionDate,
+    String? remark,
+  }) = _UpdateEquipmentRequest;
+
+  factory UpdateEquipmentRequest.fromJson(Map<String, dynamic> json) =>
+      _$UpdateEquipmentRequestFromJson(json);
+}