Enhance API and error handling for video services

- Updated .gitignore to exclude cache files.
- Refactored main.go to streamline route registration and improve code organization.
- Added detailed comments in auth_handler.go, video_handler.go, and service files for better clarity on request handling and service logic.
- Improved error messages in video_handler.go to provide clearer feedback to users in Chinese.
- Introduced context handling in service methods to manage request timeouts effectively.

internal/service/mini_program_service.go

@@ -9,6 +9,8 @@ import (
 )
 
 type MiniProgramService struct {
+	// service 层负责“业务能力”，通常会依赖数据库/第三方客户端等基础设施。
+	// 这里通过结构体字段持有 db（依赖注入），而不是在方法里自己创建连接。
 	db *gorm.DB
 }
 
@@ -17,6 +19,7 @@ func NewMiniProgramService(db *gorm.DB) *MiniProgramService {
 }
 
 func (s *MiniProgramService) GetByID(ctx context.Context, id uint) (*model.MiniProgram, error) {
+	// WithContext(ctx) 能把请求的超时/取消信号传递给数据库层，避免慢请求一直挂着。
 	var mp model.MiniProgram
 	if err := s.db.WithContext(ctx).Where("id = ?", id).First(&mp).Error; err != nil {
 		return nil, err