feat: spin-mobile — Flutter WebView 셸 (Android·iOS)

prod 웹앱(spin.special-partners.com)을 감싸는 네이티브 셸. 화면 개발 없음.
- InAppWebView: 쿠키/캐시 영속·UA(spinApp) 태그·풀투리프레시·외부링크 분기·오프라인 화면
- Android 하드웨어 뒤로가기(웹 히스토리→더블탭 종료), navy 스플래시/상태바
- 파일/카메라 업로드 권한(Android/iOS), 생체인증 잠금(local_auth)
- FCM 푸시(firebase_messaging) — 설정 전 자동 비활성, 토큰은 웹 세션으로 /api/devices 등록
- prod URL 고정(app_config.dart)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,45 @@
+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.build/
+.buildlog/
+.history
+.svn/
+.swiftpm/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins-dependencies
+.pub-cache/
+.pub/
+/build/
+/coverage/
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release