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/handler/auth_handler.go

@@ -11,6 +11,10 @@ import (
 )
 
 type AuthHandler struct {
+	// handler 层通常只做“协议转换”：
+	// - 把 HTTP 请求（JSON/header 等）解析成结构体
+	// - 调用 service 完成业务逻辑
+	// - 把结果/错误转换成统一的 JSON 响应
 	authService *service.AuthService
 }
 
@@ -21,21 +25,30 @@ func NewAuthHandler(authService *service.AuthService) *AuthHandler {
 }
 
 type weChatLoginRequest struct {
+	// binding:"required" 是 Gin 的校验标签：字段缺失或为空会导致 ShouldBindJSON 返回错误
 	MiniProgramID uint   `json:"mini_program_id" binding:"required"`
 	Code          string `json:"code" binding:"required"`
 	NickName      string `json:"nickname"`
 	AvatarURL     string `json:"avatar_url"`
-	Gender        *int   `json:"gender"`
-	Phone         string `json:"phone"`
+	// 使用 *int 可以区分：
+	// - nil：前端没传 gender
+	// - 非 nil：前端传了具体值（即使是 0）
+	Gender *int   `json:"gender"`
+	Phone  string `json:"phone"`
 }
 
 func (h *AuthHandler) LoginWithWeChat(c *gin.Context) {
+	// gin.Context 是每个请求的上下文对象：
+	// - c.Request.Context() 是标准库 context，用于把超时/取消信号传递到 DB/HTTP 调用
+	// - c.JSON(...) 用于写 JSON 响应
 	var req weChatLoginRequest
+	// ShouldBindJSON 会从请求体 JSON 反序列化到结构体，并根据 binding 标签做基础校验
 	if err := c.ShouldBindJSON(&req); err != nil {
 		c.JSON(http.StatusBadRequest, model.Error(http.StatusBadRequest, "invalid request payload"))
 		return
 	}
 
+	// 业务逻辑下沉到 service：这样 handler 更薄、更容易测试
 	result, err := h.authService.LoginWithCode(c.Request.Context(), service.LoginRequest{
 		MiniProgramID: req.MiniProgramID,
 		Code:          req.Code,