fix: 测试包年商品改用 USD，避免 CNY 不被支持

Waffo 测试侧 Yearly Product 仅支持 USD；按 Product ID 自动选币种。

backend/internal/service/payment/waffo.go

@@ -456,22 +456,36 @@ func productIDForPlan(cfg WaffoConfig, planType string) string {
 }
 
 func currencyForPlan(cfg WaffoConfig, planType string) string {
+	// 已知商品 ID 优先（测试包年不支持 CNY） // Logan.Li
+	if pid := productIDForPlan(cfg, planType); pid != "" {
+		switch pid {
+		case "PROD_1BIezCi932IbgCzRIV8hcJ", // test yearly
+			"PROD_0pcnzzT4nalEkkcdyIUoD5", // test perpetual
+			"PROD_3BSJqDRkVBoYNgO78NsTAU": // live perpetual
+			return "USD"
+		case "PROD_5PqVJyEiCM4nDgVoA0RKjN": // live yearly
+			return "CNY"
+		}
+	}
 	switch strings.TrimSpace(strings.ToLower(planType)) {
 	case "yearly", "monthly":
 		if cfg.CurrencyYearly != "" {
 			return cfg.CurrencyYearly
 		}
-		return "CNY" // OpsXshell 包年默认人民币 // Logan.Li
+		if NormalizeWaffoEnvironment(cfg.Environment) == "live" {
+			return "CNY"
+		}
+		return "USD"
 	case "perpetual", "lifetime":
 		if cfg.CurrencyPerpetual != "" {
 			return cfg.CurrencyPerpetual
 		}
-		return "USD" // OpsXshell 永久默认美元 // Logan.Li
+		return "USD"
 	}
 	if cfg.Currency != "" {
 		return cfg.Currency
 	}
-	return "CNY"
+	return "USD"
 }
 
 func checkoutTypeForPlan(planType string) string {