docs: standardize English as the default language and add Chinese localization files

fix(websocket): prefer direct port URL when WS_EXTERNAL_PORT is configured

fix(agent): service-aware start/stop/restart and systemd Restart=always

feat: Implement country name internationalization using `Intl.DisplayNames` and fix desktop scrollbar layout shift.

feat: Extend WebSocket summary with total proxies and rules, refine dashboard data fetching during WebSocket connection, and add a new logo.

feat: Implement `useResponsiveItemCount` for dynamic overview list display and add traffic progress bars to top domains.

feat: Release version 1.3.4 with enhanced backend health monitoring, agent auto-start, WebSocket optimizations, and minor fixes.

feat: Implement granular summary data fetching and caching, and enable summary totals for the dashboard rules tab.

feat: Implement selective summary field retrieval for WebSocket stats to optimize data transfer.

feat: Add `includeSummary` parameter to WebSocket stats, round `useStableTimeRange` to the nearest minute, and refine WebSocket detail subscription conditions.

refactor: update `tr` command usage for case conversion and prevent redundant manager file synchronization.

feat: Implement agent autostart functionality using system service managers (systemd, launchd, OpenWrt, cron).

feat: Dynamically display latency or online status in the backend health chart, refine latency calculation, and localize gateway/server labels.

feat: Add server latency reporting and monitoring for backend health.

feat: Improve backend health monitoring with explicit status, latency-based chart coloring, and robust heartbeat data updates.