refactor: localize tray menu items to Chinese

Rename the menu bar items to 截图 / 设置 / 退出 for the primary Chinese
audience.

frontend/src/App.vue

@@ -64,10 +64,10 @@ const activeTab = ref<SettingsTab>('general')
 // Sidebar entries are declarative so adding a destination type later is
 // a one-line change. The label values match the user-facing tab names.
 const sidebarItems: Array<{ id: SettingsTab; label: string }> = [
-  { id: 'general', label: 'General' },
-  { id: 's3', label: 'S3' },
-  { id: 'ssh', label: 'SSH' },
-  { id: 'llm', label: 'LLM' },
+  { id: 'general', label: '通用设置' },
+  { id: 's3', label: '对象存储' },
+  { id: 'ssh', label: '远程主机' },
+  { id: 'llm', label: '智能识图' },
 ]
 
 interface OverlayPayload {

internal/infrastructure/tray/tray.go

@@ -33,10 +33,10 @@ func Start(cbs Callbacks) (start, stop func()) {
 		systray.SetTemplateIcon(templateIconBytes, regularIconBytes)
 		systray.SetTooltip("SnapGo")
 
-		mCapture := systray.AddMenuItem("Capture screenshot", "Take a region screenshot")
-		mSettings := systray.AddMenuItem("Settings…", "Open settings window")
+		mCapture := systray.AddMenuItem("截图", "Take a region screenshot")
+		mSettings := systray.AddMenuItem("设置", "Open settings window")
 		systray.AddSeparator()
-		mQuit := systray.AddMenuItem("Quit SnapGo", "Quit the application")
+		mQuit := systray.AddMenuItem("退出", "Quit the application")
 
 		// Pump menu clicks on a dedicated goroutine. Channel sends from
 		// systray are non-blocking, so a slow user callback does not back