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/middleware/auth_middleware.go

@@ -13,6 +13,10 @@ import (
 const ContextCurrentUserKey = "currentUser"
 
 func AuthMiddleware(db *gorm.DB) gin.HandlerFunc {
+	// AuthMiddleware 是一个 Gin 中间件：
+	// - 从 Authorization: Bearer <token> 里取 token
+	// - 用 token（这里是 session_key）查用户
+	// - 查到后放进 gin.Context，供后面的 handler 使用
 	return func(c *gin.Context) {
 		token := extractToken(c.GetHeader("Authorization"))
 		if token == "" {
@@ -36,6 +40,7 @@ func AuthMiddleware(db *gorm.DB) gin.HandlerFunc {
 }
 
 func extractToken(authHeader string) string {
+	// 常见格式：Authorization: Bearer <token>
 	if authHeader == "" {
 		return ""
 	}