feat: 회사 관리 기능 개선 및 지점 평면화 DTO 추가

- CompanyBranchFlatDto 모델 추가로 지점 데이터 처리 개선
- 회사 서비스에 브랜치 평면화 기능 추가
- 회사 폼 컨트롤러 기능 확장
- 회사 리스트 화면 UI 개선

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

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

lib/data/datasources/remote/company_remote_datasource.dart

@@ -9,6 +9,7 @@ import 'package:superport/data/models/common/paginated_response.dart';
 import 'package:superport/data/models/company/company_dto.dart';
 import 'package:superport/data/models/company/company_list_dto.dart';
 import 'package:superport/data/models/company/branch_dto.dart';
+import 'package:superport/data/models/company/company_branch_flat_dto.dart';
 
 abstract class CompanyRemoteDataSource {
   Future<PaginatedResponse<CompanyListDto>> getCompanies({
@@ -48,6 +49,8 @@ abstract class CompanyRemoteDataSource {
   Future<void> deleteBranch(int companyId, int branchId);
   
   Future<List<BranchListDto>> getCompanyBranches(int companyId);
+  
+  Future<List<CompanyBranchFlatDto>> getCompanyBranchesFlat();
 }
 
 @LazySingleton(as: CompanyRemoteDataSource)
@@ -343,6 +346,36 @@ class CompanyRemoteDataSourceImpl implements CompanyRemoteDataSource {
     }
   }
   
+  @override
+  Future<List<CompanyBranchFlatDto>> getCompanyBranchesFlat() async {
+    try {
+      final response = await _apiClient.get('${ApiEndpoints.companies}/branches');
+      
+      if (response.statusCode == 200) {
+        final responseData = response.data;
+        if (responseData != null && responseData['success'] == true && responseData['data'] != null) {
+          final List<dynamic> dataList = responseData['data'];
+          return dataList.map((item) => 
+            CompanyBranchFlatDto.fromJson(item as Map<String, dynamic>)
+          ).toList();
+        } else {
+          throw ApiException(
+            message: responseData?['error']?['message'] ?? 'Failed to load company branches',
+            statusCode: response.statusCode,
+          );
+        }
+      } else {
+        throw ApiException(
+          message: 'Failed to load company branches',
+          statusCode: response.statusCode,
+        );
+      }
+    } catch (e) {
+      if (e is ApiException) rethrow;
+      throw ApiException(message: e.toString());
+    }
+  }
+  
   @override
   Future<bool> checkDuplicateCompany(String name) async {
     try {