fix(deps): 降级 share_plus 版本修复 Android 构建错误

将 share_plus 从 ^10.0.0 降级到 ^7.2.2，解决 Android SDK 35 构建时的 Kotlin 编译错误

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mobile-app/pubspec.yaml

@@ -54,7 +54,7 @@ dependencies:
   image_picker: ^1.0.7
   permission_handler: ^11.3.1
   url_launcher: ^6.2.6
-  share_plus: ^10.0.0
+  share_plus: ^7.2.2
 
   # 生物识别
   local_auth: ^2.2.0