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

test/components/AiProviderSettings.test.tsx

@@ -33,11 +33,11 @@ describe('AI provider settings', () => {
     expect(save).toBeDisabled()
 
     fireEvent.change(screen.getByLabelText('API Key'), { target: { value: 'sk-test-only' } })
-    fireEvent.click(screen.getByRole('button', { name: '测试连接' }))
+    fireEvent.click(screen.getByRole('button', { name: '测试' }))
 
     await waitFor(() => expect(mockDesktopApi.aiTestProvider).toHaveBeenCalled())
     expect(mockDesktopApi.aiProviderSaveKey).not.toHaveBeenCalled()
-    expect(await screen.findByText(/测试成功 · HTTP 200/)).toBeVisible()
+    expect(await screen.findByText(/可用/)).toBeVisible()
     expect(save).toBeEnabled()
 
     fireEvent.click(save)
@@ -50,12 +50,13 @@ describe('AI provider settings', () => {
     render(<AiProviderSettings />)
     fireEvent.click(screen.getByRole('button', { name: '添加' }))
     fireEvent.change(screen.getByLabelText('API Key'), { target: { value: 'sk-test-only' } })
-    fireEvent.click(screen.getByRole('button', { name: '测试连接' }))
+    fireEvent.click(screen.getByRole('button', { name: '测试' }))
     const save = screen.getByRole('button', { name: '保存' })
     await waitFor(() => expect(save).toBeEnabled())
 
+    fireEvent.click(screen.getByRole('button', { name: '高级' }))
     fireEvent.change(screen.getByLabelText('Endpoint'), { target: { value: 'https://proxy.example.com/v1' } })
     expect(save).toBeDisabled()
-    expect(screen.getByText('连接字段已变更，请重新测试')).toBeVisible()
+    expect(screen.getByText('请重新测试')).toBeVisible()
   })
 })