test: 통합 테스트 오류 및 경고 수정

- 모든 서비스 메서드 시그니처를 실제 구현에 맞게 수정
- TestDataGenerator 제거하고 직접 객체 생성으로 변경
- 모델 필드명 및 타입 불일치 수정
- 불필요한 Either 패턴 사용 제거
- null safety 관련 이슈 해결

수정된 파일:
- test/integration/screens/company_integration_test.dart
- test/integration/screens/equipment_integration_test.dart
- test/integration/screens/user_integration_test.dart
- test/integration/screens/login_integration_test.dart

lib/data/models/auth/login_request.freezed.dart

@@ -20,7 +20,9 @@ LoginRequest _$LoginRequestFromJson(Map<String, dynamic> json) {
 
 /// @nodoc
 mixin _$LoginRequest {
+  @JsonKey(includeIfNull: false)
   String? get username => throw _privateConstructorUsedError;
+  @JsonKey(includeIfNull: false)
   String? get email => throw _privateConstructorUsedError;
   String get password => throw _privateConstructorUsedError;
 
@@ -40,7 +42,10 @@ abstract class $LoginRequestCopyWith<$Res> {
           LoginRequest value, $Res Function(LoginRequest) then) =
       _$LoginRequestCopyWithImpl<$Res, LoginRequest>;
   @useResult
-  $Res call({String? username, String? email, String password});
+  $Res call(
+      {@JsonKey(includeIfNull: false) String? username,
+      @JsonKey(includeIfNull: false) String? email,
+      String password});
 }
 
 /// @nodoc
@@ -87,7 +92,10 @@ abstract class _$$LoginRequestImplCopyWith<$Res>
       __$$LoginRequestImplCopyWithImpl<$Res>;
   @override
   @useResult
-  $Res call({String? username, String? email, String password});
+  $Res call(
+      {@JsonKey(includeIfNull: false) String? username,
+      @JsonKey(includeIfNull: false) String? email,
+      String password});
 }
 
 /// @nodoc
@@ -127,14 +135,19 @@ class __$$LoginRequestImplCopyWithImpl<$Res>
 /// @nodoc
 @JsonSerializable()
 class _$LoginRequestImpl implements _LoginRequest {
-  const _$LoginRequestImpl({this.username, this.email, required this.password});
+  const _$LoginRequestImpl(
+      {@JsonKey(includeIfNull: false) this.username,
+      @JsonKey(includeIfNull: false) this.email,
+      required this.password});
 
   factory _$LoginRequestImpl.fromJson(Map<String, dynamic> json) =>
       _$$LoginRequestImplFromJson(json);
 
   @override
+  @JsonKey(includeIfNull: false)
   final String? username;
   @override
+  @JsonKey(includeIfNull: false)
   final String? email;
   @override
   final String password;
@@ -178,16 +191,18 @@ class _$LoginRequestImpl implements _LoginRequest {
 
 abstract class _LoginRequest implements LoginRequest {
   const factory _LoginRequest(
-      {final String? username,
-      final String? email,
+      {@JsonKey(includeIfNull: false) final String? username,
+      @JsonKey(includeIfNull: false) final String? email,
       required final String password}) = _$LoginRequestImpl;
 
   factory _LoginRequest.fromJson(Map<String, dynamic> json) =
       _$LoginRequestImpl.fromJson;
 
   @override
+  @JsonKey(includeIfNull: false)
   String? get username;
   @override
+  @JsonKey(includeIfNull: false)
   String? get email;
   @override
   String get password;