fix(tenant-service): packageName 改为可选参数，兼容旧版 SDK

旧版 sdk-core 的 fetchConfig 未传 packageName，服务端返回 400
导致 bugCollectEnabled 始终为 false，captureError 静默失败。

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

tenant-service/src/main/java/com/xuqm/tenant/controller/SdkConfigController.java

@@ -61,7 +61,7 @@ public class SdkConfigController {
     @GetMapping("/config")
     public ResponseEntity<ApiResponse<SdkConfigResponse>> getConfig(
             @RequestParam String appKey,
-            @RequestParam String packageName,
+            @RequestParam(required = false, defaultValue = "") String packageName,
             @RequestParam(required = false, defaultValue = "ANDROID") FeatureServiceEntity.Platform platform) {
 
         AppEntity app = sdkAppProvisioningService.resolveApp(appKey);