Optimize Dockerfile cache, binary size, SQLite WAL, and remove unused python package

backend/models/db.go

@@ -39,6 +39,9 @@ func InitDB(dbPath string) {
 		log.Fatal("Failed to connect to database:", err)
 	}
 
+	// SQLite 동시성 최적화를 위해 WAL(Write-Ahead Logging) 모드를 활성화
+	DB.Exec("PRAGMA journal_mode=WAL;")
+
 	err = DB.AutoMigrate(&MediaHistory{})
 	if err != nil {
 		log.Println("Database migration error:", err)