feat(i18n): add multi-language support (ja/ko/vi/ru/zh-TW) with system auto-detection

- Extend AppLanguage to 7 locales: zh-CN, zh-TW, en, ja, ko, vi, ru
- Auto-detect system language via navigator.languages; fallback to English
- Add BCP47 locale mapping for date formatting and sorting
- Create 50 translation JSON files (5 languages × 10 namespaces, 1137 keys each)
- Update language selector with native language names
- Extend locale key parity test to cover all 7 languages (70 assertions)
- Add VNC/RDP desktop, serial terminal, AI agent, port forwarding, and SFTP features
- Add credential encryption, host metrics, session backup crypto, and zmodem bridge
- Update Rust backend: desktop services, host metrics, SSH/SFTP enhancements

src/components/layout/tabbar/TabContextMenu.tsx

@@ -3,6 +3,7 @@
  */
 
 import { useRef, useEffect } from 'react'
+import { useTranslation } from 'react-i18next'
 
 interface MenuItem {
   label: string
@@ -34,6 +35,7 @@ export function TabContextMenu({
   onCloseAll,
   onClone,
 }: TabContextMenuProps) {
+  const { t } = useTranslation('common')
   const menuRef = useRef<HTMLDivElement>(null)
 
   useEffect(() => {
@@ -49,15 +51,15 @@ export function TabContextMenu({
   if (!isOpen) return null
 
   const items: MenuItem[] = [
-    { label: '关闭', action: onCloseTab },
-    { label: '关闭其他', action: onCloseOthers },
-    { label: '关闭右侧标签', action: onCloseRight },
-    { label: '关闭左侧标签', action: onCloseLeft },
-    { label: '关闭全部', action: onCloseAll, danger: true },
+    { label: t('action.close'), action: onCloseTab },
+    { label: t('tab.menu.closeOthers'), action: onCloseOthers },
+    { label: t('tab.menu.closeRight'), action: onCloseRight },
+    { label: t('tab.menu.closeLeft'), action: onCloseLeft },
+    { label: t('tab.menu.closeAll'), action: onCloseAll, danger: true },
   ]
 
   if (onClone) {
-    items.unshift({ label: '克隆标签', action: onClone })
+    items.unshift({ label: t('tab.menu.clone'), action: onClone })
   }
 
   return (