feat(v2): 多币种 product(ProductPrice 分币价目 + v1 元回退)+ 结算币种由渠道能力驱动

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nMthbVEmQquxBRKb9Fj8u

internal/handler/gateway_test.go

@@ -25,8 +25,8 @@ func (nopEnqueuer) Enqueue(string, string, string, map[string]any) error { retur
 
 type oneResolver struct{}
 
-func (oneResolver) Resolve(sku string) (int64, string, string, string, error) {
-	return 29990000, "USDT", "Pro 年付", "pro_year", nil
+func (oneResolver) Resolve(sku, currency string) (int64, string, string, error) {
+	return 29990000, "Pro 年付", "pro_year", nil
 }
 
 func buildEngine(t *testing.T) *gin.Engine {