feat: 添加生产环境部署工作流和相关文档

backend/cmd/server/main.go

@@ -29,15 +29,22 @@ func run() error {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 
-	for _, key := range []string{"PGHOST", "PGDATABASE", "PGUSER", "PGPASSWORD"} {
-		if os.Getenv(key) == "" {
-			return fmt.Errorf("%s is required", key)
+	databaseURL := os.Getenv("DATABASE_URL")
+	if databaseURL == "" {
+		for _, key := range []string{"PGHOST", "PGDATABASE", "PGUSER", "PGPASSWORD"} {
+			if os.Getenv(key) == "" {
+				return fmt.Errorf("%s is required when DATABASE_URL is unset", key)
+			}
 		}
 	}
 
-	// Use libpq environment variables so passwords need no URL escaping.
-	pool, err := pgxpool.New(ctx, "")
+	// Production uses a URL; local development retains libpq environment variables.
+	pool, err := pgxpool.New(ctx, databaseURL)
 	if err != nil {
+		if databaseURL != "" {
+			// Parser errors can include the URL, so do not log the credential-bearing input.
+			return errors.New("configure database: invalid DATABASE_URL")
+		}
 		return fmt.Errorf("configure database: %w", err)
 	}
 	defer pool.Close()