perf: 优化后端性能与直播延迟，包含数据库WAL模式、流媒体写缓冲、转码 Preset 优化、聊天锁和指标采集优化，以及前端自动追帧功能

backend/internal/db/db.go

@@ -29,14 +29,23 @@ func InitDB() {
 	)
 
 	var err error
-	// Use SQLite database stored in a local file named "hightube.db"
-	DB, err = gorm.Open(sqlite.Open("hightube.db"), &gorm.Config{
+	// Use SQLite database stored in a local file named "hightube.db" with WAL mode and busy timeout enabled
+	DB, err = gorm.Open(sqlite.Open("hightube.db?_journal_mode=WAL&_busy_timeout=5000"), &gorm.Config{
 		Logger: newLogger,
 	})
 	if err != nil {
 		log.Fatalf("Failed to connect database: %v", err)
 	}
 
+	// Configure connection pool settings
+	sqlDB, err := DB.DB()
+	if err != nil {
+		log.Fatalf("Failed to get database instance: %v", err)
+	}
+	sqlDB.SetMaxOpenConns(10)
+	sqlDB.SetMaxIdleConns(5)
+	sqlDB.SetConnMaxLifetime(time.Hour)
+
 	// Auto-migrate the schema
 	err = DB.AutoMigrate(&model.User{}, &model.Room{})
 	if err != nil {
@@ -48,7 +57,7 @@ func InitDB() {
 
 	ensureAdminUser()
 
-	monitor.Infof("Database initialized successfully")
+	monitor.Infof("Database initialized successfully with WAL mode and connection pooling")
 }
 
 func ensureAdminUser() {