♻️ refactor(file): 修改文件实体日期字段类型

- 将upload_time字段类型从datetime改为timestamp
- 将last_updated字段类型从datetime改为timestamp
- 统一日期字段类型以提高数据库兼容性和查询性能

src/server/modules/files/file.entity.ts

@@ -61,10 +61,10 @@ export class File {
   @JoinColumn({ name: 'upload_user_id', referencedColumnName: 'id' })
   uploadUser!: UserEntity;
 
-  @Column({ name: 'upload_time', type: 'datetime' })
+  @Column({ name: 'upload_time', type: 'timestamp' })
   uploadTime!: Date;
 
-  @Column({ name: 'last_updated', type: 'datetime', nullable: true, comment: '最后更新时间' })
+  @Column({ name: 'last_updated', type: 'timestamp', nullable: true, comment: '最后更新时间' })
   lastUpdated!: Date | null;
 
   @Column({ name: 'created_at', type: 'timestamp', default: () => 'CURRENT_TIMESTAMP' })