fix: 修复函数签名变更后的调用参数不匹配

- handleUpstreamError 补齐新增的三个参数 (0, "", false)
- handleStreamingResponse 移除已删除的 nil 参数

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/internal/service/antigravity_gateway_service.go

@@ -1650,7 +1650,7 @@ func (s *AntigravityGatewayService) ForwardUpstream(ctx context.Context, c *gin.
 
 		// 429 错误时标记账号限流
 		if resp.StatusCode == http.StatusTooManyRequests {
-			s.handleUpstreamError(ctx, prefix, account, resp.StatusCode, resp.Header, respBody, AntigravityQuotaScopeClaude)
+			s.handleUpstreamError(ctx, prefix, account, resp.StatusCode, resp.Header, respBody, AntigravityQuotaScopeClaude, 0, "", false)
 		}
 
 		// 透传上游错误