feat(auth): add Casbin RBAC and user activity tracking

Integrate Casbin for role-based access control with admin routes for role management. Add user activity logging service to track login and refresh events. Refactor audit service to use AI-based content moderation.

internal/config/casbin.go

@@ -0,0 +1,22 @@
+package config
+
+// CasbinConfig Casbin 配置
+type CasbinConfig struct {
+	// ModelPath Casbin 模型文件路径
+	ModelPath string `mapstructure:"model_path"`
+
+	// AutoSave 是否自动保存策略到数据库
+	AutoSave bool `mapstructure:"auto_save"`
+
+	// AutoLoad 是否自动从数据库加载策略
+	AutoLoad bool `mapstructure:"auto_load"`
+
+	// EnableCache 是否启用 Redis 缓存
+	EnableCache bool `mapstructure:"enable_cache"`
+
+	// CacheTTL 缓存过期时间 (秒)
+	CacheTTL int `mapstructure:"cache_ttl"`
+
+	// SkipRoutes 跳过权限检查的路由
+	SkipRoutes []string `mapstructure:"skip_routes"`
+}