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/sftp/SortHeader.tsx

@@ -3,6 +3,7 @@
  */
 
 import { ArrowUp, ArrowDown } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import type { SortField, SortOrder } from '../../../shared/types/sftp.types'
 
 interface SortHeaderProps {
@@ -11,17 +12,19 @@ interface SortHeaderProps {
   sortOrder: SortOrder
 }
 
-const FIELDS: { key: SortField; label: string; className: string }[] = [
-  { key: 'name', label: '名称', className: 'flex-1 min-w-0 justify-start' },
-  { key: 'modified', label: '修改时间', className: 'w-32 justify-end' },
-  { key: 'size', label: '大小', className: 'w-24 justify-end' },
-  { key: 'type', label: '类型', className: 'w-24 justify-end' },
+const FIELDS: { key: SortField; className: string }[] = [
+  { key: 'name', className: 'flex-1 min-w-0 justify-start' },
+  { key: 'modified', className: 'w-32 justify-end' },
+  { key: 'size', className: 'w-24 justify-end' },
+  { key: 'type', className: 'w-24 justify-end' },
 ]
 
 export function SortHeader({ onSort, sortField, sortOrder }: SortHeaderProps) {
+  const { t } = useTranslation('sftp')
+
   return (
     <div className="h-8 flex items-center w-full text-xs text-txt-muted select-none">
-      {FIELDS.map(({ key, label, className }) => {
+      {FIELDS.map(({ key, className }) => {
         const active = sortField === key
         return (
           <button
@@ -32,7 +35,7 @@ export function SortHeader({ onSort, sortField, sortOrder }: SortHeaderProps) {
               active ? 'text-content-primary' : ''
             }`}
           >
-            <span>{label}</span>
+            <span>{t(`sort.${key}`)}</span>
             {active &&
               (sortOrder === 'asc' ? (
                 <ArrowUp className="w-3 h-3 flex-shrink-0" />