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>

.metadata

@@ -0,0 +1,33 @@
+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: "ad70ec4617166f1c38e5d2bfd388af71fda14f06"
+  channel: "stable"
+
+project_type: app
+
+# Tracks metadata for the flutter migrate command
+migration:
+  platforms:
+    - platform: root
+      create_revision: ad70ec4617166f1c38e5d2bfd388af71fda14f06
+      base_revision: ad70ec4617166f1c38e5d2bfd388af71fda14f06
+    - platform: android
+      create_revision: ad70ec4617166f1c38e5d2bfd388af71fda14f06
+      base_revision: ad70ec4617166f1c38e5d2bfd388af71fda14f06
+    - platform: ios
+      create_revision: ad70ec4617166f1c38e5d2bfd388af71fda14f06
+      base_revision: ad70ec4617166f1c38e5d2bfd388af71fda14f06
+
+  # User provided section
+
+  # List of Local paths (relative to this file) that should be
+  # ignored by the migrate tool.
+  #
+  # Files that are not part of the templates will be ignored by default.
+  unmanaged_files:
+    - 'lib/main.dart'
+    - 'ios/Runner.xcodeproj/project.pbxproj'