feat(mobile): flutter scaffold with env script and baseline nav

- scripts/flutter-env.sh: toolchain PATH/JAVA_HOME/ANDROID_HOME + pub 镜像 env
- apps/mobile: flutter create (com.photolive.photo_live, android+ios)
  - Android minSdk 24 / targetSdk 36；INTERNET 权限（main manifest，debug+release）
  - iOS Info.plist：本地网络 ATS 例外 + 相册/相机用途说明（zh+en）
- 依赖接入：riverpod / drift(+sqlite3_flutter_libs) / dio / secure_storage /
  image_picker / camera / qr_flutter / path_provider / path / intl
- l10n：l10n.yaml + app_zh/app_en arb（20 键），gen-l10n（zh 模板，非空 getter）
- 基线：Material 3 主题、/login→/home 命名路由、底部导航（相册/队列/设置桩）、
  locale provider 脚手架（Task 10 完成切换）
- flutter analyze 零问题；widget 测试通过；debug apk 构建成功
  （MuMu 冒烟因宿主 commit 内存耗尽未完成，Task 2 重试）

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

apps/mobile/.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