feat: 支持Android返回键退出确认与多语言提示

新增Android端返回键退出确认弹窗，防止误触直接退出应用。各语言包补充退出确认标题与提示语，提升多语言体验。依赖新增@capacitor/app，样式与主题适配同步优化。

src/locales/en.ts

@@ -45,7 +45,9 @@ export default {
     current: 'Current',
     level: 'Level',
     gmModeActivated: 'GM Mode Activated! Check the navigation menu.',
-    view: 'View'
+    view: 'View',
+    exitConfirmTitle: 'Exit Game',
+    exitConfirmMessage: 'Are you sure you want to exit? Your progress is saved automatically.'
   },
   errors: {
     requirementsNotMet: 'Requirements not met',