✅ test(file): fix file service test mock implementation

- refactor mock implementation for MinioService to use mock function directly
- update test assertion to use mockGenerateUploadPolicy instead of mockMinioService
- ensure proper tracking of generateUploadPolicy method calls in tests

src/server/modules/files/__tests__/file.service.test.ts

@@ -56,15 +56,17 @@ describe('FileService', () => {
         updatedAt: new Date()
       };
 
-      // Mock MinioService
-      vi.mocked(mockMinioService.generateUploadPolicy).mockResolvedValue(mockUploadPolicy);
+      const mockGenerateUploadPolicy = vi.fn().mockResolvedValue(mockUploadPolicy);
+      vi.mocked(MinioService).mockImplementation(() => ({
+        generateUploadPolicy: mockGenerateUploadPolicy
+      } as unknown as MinioService));
 
       // Mock GenericCrudService methods
       vi.spyOn(fileService, 'create').mockResolvedValue(mockSavedFile as File);
 
       const result = await fileService.createFile(mockFileData);
 
-      expect(mockMinioService.generateUploadPolicy).toHaveBeenCalledWith('1/test-uuid-123-test.txt');
+      expect(mockGenerateUploadPolicy).toHaveBeenCalledWith('1/test-uuid-123-test.txt');
       expect(fileService.create).toHaveBeenCalledWith(expect.objectContaining({
         name: 'test.txt',
         path: '1/test-uuid-123-test.txt',