feat: auto-backup UI and window close hook

src/App.vue

@@ -188,6 +188,23 @@ onMounted(async () => {
 
   registerShortcuts()
 
+  // Auto-backup on window close
+  try {
+    const { getCurrentWindow } = await import('@tauri-apps/api/window')
+    const win = getCurrentWindow()
+    win.onCloseRequested(async () => {
+      if (settingsStore.settings.auto_backup === 'true' && settingsStore.settings.backup_path) {
+        try {
+          await invoke('auto_backup', { backupDir: settingsStore.settings.backup_path })
+        } catch (e) {
+          console.error('Auto-backup failed:', e)
+        }
+      }
+    })
+  } catch (e) {
+    console.error('Failed to register close handler:', e)
+  }
+
   window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', () => {
     if (settingsStore.settings.theme_mode === 'system') applyTheme()
   })