feat: 添加数据库迁移工具并创建AI记账服务文件。

cmd/migrate/main.go

@@ -14,12 +14,12 @@ import (
 func main() {
 	// Load .env file from project root (try multiple locations)
 	envPaths := []string{
-		".env",                          // Current directory
-		"../.env",                        // Parent directory (when running from backend/)
-		"../../.env",                     // Two levels up (when running from backend/cmd/migrate/)
+		".env",                            // Current directory
+		"../.env",                         // Parent directory (when running from backend/)
+		"../../.env",                      // Two levels up (when running from backend/cmd/migrate/)
 		filepath.Join("..", "..", ".env"), // Explicit path
 	}
-	
+
 	for _, envPath := range envPaths {
 		if err := godotenv.Load(envPath); err == nil {
 			log.Printf("Loaded environment from: %s", envPath)