feat: new pages + dashboard enhancements + backend improvements

New pages:
- Plugin Hub: grid cards, search, install/toggle/enable plugins
- Route Map: SVG visualization of channels→agents bindings with legends
- Diagnose: gateway connectivity diagnosis with step-by-step checks

Dashboard enhancements:
- WebSocket status indicator (connected/handshaking/reconnecting/disconnected)
- Connected channels overview with platform icons
- Colored log level badges (ERROR/WARN/INFO/DEBUG) with timestamps
- Channels data loading in dashboard secondary fetch

Splash screen:
- Multi-stage boot detection (JS not loaded vs boot slow vs timeout)
- 15s: WebView2/resource load failure
- 20s: "initializing..." hint with elapsed counter
- 90s: true timeout error

Backend (Rust):
- diagnose.rs: gateway connectivity diagnosis command
- messaging.rs: plugin management commands
- service.rs: improvements
- lib.rs: register new commands

Frontend libs:
- feature-gates.js: feature flag system
- ws-client.js: reconnect state tracking
- tauri-api.js: new API bindings
- model-presets.js: provider fixes
- Remove gateway-guardian-policy.js (unused)

Dev API (scripts/dev-api.js):
- list_all_plugins, toggle_plugin, install_plugin handlers
- probe_gateway_port, diagnose_gateway_connection handlers

i18n: dashboard, sidebar, diagnose, extensions, routeMap locale modules
CSS: plugin-hub cards, route-map SVG styles

src-tauri/src/lib.rs

@@ -4,8 +4,8 @@ mod tray;
 mod utils;
 
 use commands::{
-    agent, assistant, config, device, extensions, logs, memory, messaging, pairing, service,
-    skills, update,
+    agent, assistant, config, device, diagnose, extensions, logs, memory, messaging, pairing,
+    service, skills, update,
 };
 
 pub fn run() {
@@ -125,7 +125,10 @@ pub fn run() {
             service::stop_service,
             service::restart_service,
             service::claim_gateway,
+            service::probe_gateway_port,
             service::guardian_status,
+            // 诊断
+            diagnose::diagnose_gateway_connection,
             // 日志
             logs::read_log_tail,
             logs::search_log,
@@ -183,6 +186,9 @@ pub fn run() {
             messaging::repair_qqbot_channel_setup,
             messaging::list_configured_platforms,
             messaging::get_channel_plugin_status,
+            messaging::list_all_plugins,
+            messaging::toggle_plugin,
+            messaging::install_plugin,
             messaging::install_channel_plugin,
             messaging::install_qqbot_plugin,
             messaging::run_channel_action,