Enhance AI and Redis integration for smoke logging features

- Added AI configuration options to .env.example and config.go for OpenAI integration.
- Implemented Redis caching for session management in main.go and auth middleware.
- Updated smoke logging service to support real smoking time (`smoke_at`) and AI advice retrieval.
- Enhanced API routes to include endpoints for AI advice and unlock functionality for non-members.
- Improved database schema with new tables for AI advice and unlock records.
- Expanded documentation to cover new AI features and Redis caching implementation.

internal/smoke/model/smoke_log.go

@@ -13,6 +13,8 @@ type SmokeLog struct {
 
 	// smoke_time 在库里是 date 类型（只包含日期，不包含时分秒）。
 	SmokeTime *time.Time `gorm:"column:smoke_time;type:date" json:"smoke_time,omitempty"`
+	// smoke_at：真实抽烟时间（可补录，精确到时分秒）
+	SmokeAt *time.Time `gorm:"column:smoke_at;type:datetime" json:"smoke_at,omitempty"`
 
 	Remark string `gorm:"column:remark;type:text" json:"remark,omitempty"`