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/hooks/useKeyboardShortcuts.ts

@@ -22,6 +22,7 @@ import { useCommandPaletteStore } from '../stores/commandPaletteStore'
 import { useKeybindingStore } from '../stores/keybindingStore'
 import { KeybindingAction } from '../constants/keybindings'
 import { createLogger } from '../utils/logger'
+import i18n from '../i18n'
 import { disposeAndCloseTab } from '../utils/disposeTab'
 
 const logger = createLogger('KeyboardShortcuts')
@@ -231,7 +232,7 @@ export function useKeyboardShortcuts(): void {
       // ---- Ctrl+Shift+N: 新建标签 ----
       if (matchesKeySequence(e, keys[KeybindingAction.TAB_NEW])) {
         e.preventDefault()
-        useTabStore.getState().addTab({ title: '新标签', type: 'welcome' })
+        useTabStore.getState().addTab({ title: i18n.t('common:tab.new'), type: 'welcome' })
         return
       }