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/index.css

@@ -334,6 +334,28 @@ html, body {
   50% { opacity: 0.7; }
 }
 
+@keyframes pfDashFlow {
+  to {
+    stroke-dashoffset: -16;
+  }
+}
+
+@keyframes pfTunnelPulse {
+  0%,
+  100% {
+    opacity: 0.22;
+    stroke-dashoffset: 0;
+  }
+  50% {
+    opacity: 1;
+    stroke-dashoffset: -14;
+  }
+}
+
+.pf-tunnel-dash {
+  animation: pfTunnelPulse 1.35s ease-in-out infinite;
+}
+
 .animate-slide-in-right { animation: slideInRight 0.3s cubic-bezier(0.16, 1, 0.3, 1); }
 .animate-slide-out-right { animation: slideOutRight 0.2s ease-in forwards; }
 .animate-slide-in-up { animation: slideInUp 0.25s cubic-bezier(0.16, 1, 0.3, 1); }