fix(antigravity): 减少 API 转发最大重试次数至 3

backend/internal/service/antigravity_gateway_service.go

@@ -20,7 +20,7 @@ import (
 
 const (
 	antigravityStickySessionTTL = time.Hour
-	antigravityMaxRetries       = 5
+	antigravityMaxRetries       = 3
 	antigravityRetryBaseDelay   = 1 * time.Second
 	antigravityRetryMaxDelay    = 16 * time.Second
 )