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-tauri/src/services/desktop/mod.rs

@@ -0,0 +1,16 @@
+//! Remote desktop session managers (RDP / VNC).
+//!
+//! IronRDP and vnc-rs drive Canvas frames over Tauri events. Session runtime
+//! state lives only in memory; disconnect cancels the worker thread.
+
+mod cliprdr_backend;
+mod common;
+mod input_map;
+mod rdp;
+mod rdp_engine;
+mod rdpdr_fs;
+mod vnc;
+mod vnc_engine;
+
+pub use rdp::RdpService;
+pub use vnc::VncService;