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/utils/zmodemSftpBridge.test.ts

@@ -0,0 +1,24 @@
+import { describe, expect, it } from 'vitest'
+import { parseSzFiles } from '../../src/utils/zmodemSftpBridge'
+
+describe('parseSzFiles', () => {
+  it('parses simple sz command', () => {
+    expect(parseSzFiles('sz app.log\r')).toEqual(['app.log'])
+  })
+
+  it('parses multiple files and skips flags', () => {
+    expect(parseSzFiles('sz -y a.txt b.bin\n')).toEqual(['a.txt', 'b.bin'])
+  })
+
+  it('uses the latest command line', () => {
+    expect(parseSzFiles('sz old\rsz newer.tar.gz\r')).toEqual(['newer.tar.gz'])
+  })
+
+  it('returns empty when no sz command', () => {
+    expect(parseSzFiles('ls\rrz\r')).toEqual([])
+  })
+
+  it('strips bracketed-paste markers', () => {
+    expect(parseSzFiles('\x1b[200~sz report.txt\x1b[201~\r')).toEqual(['report.txt'])
+  })
+})