fix: export_method를 app-store로 복원 (gym 호환)

- gym이 app-store-connect를 지원하지 않음
- setup_ci로 키체인 문제 해결됨 → app-store로 export 가능

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

Author: boring-km

ios/fastlane/Fastfile

@@ -19,7 +19,7 @@ platform :ios do
       configuration: "Release",
       workspace: "Runner.xcworkspace",
       scheme: "Runner",
-      export_method: "app-store-connect",
+      export_method: "app-store",
       export_options: {
         teamID: "T583WJWNAK",
         provisioningProfiles: {