system-monitor: /system-monitor route (CPU/mem/disk/processes) + page titles

- Backend GET /api/system-monitor/stats: one snapshot — CPU overall + per-core
  (two /proc/stat samples), memory + swap (/proc/meminfo), disks (df), load,
  uptime, top-20 processes (ps). Owner-only via the account gate.
- Frontend /system-monitor screen: polls every 2s; CPU/Memory/Disks cards with
  bars + per-core mini-bars, top-processes table. Nav dock "Monitor" item.
- Register /music and /system-monitor in usePageTitle RULES so the browser tab
  and editable header title update on those routes (/music was missing too).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/hono.ts

@@ -20,6 +20,7 @@ import { dashboardsRouter } from './api/dashboards';
 import { taskLogsRouter } from './api/task-logs/task-logs';
 import { router as fileBrowserRouter } from './api/file-browser/router';
 import { musicRouter } from './api/music/router';
+import { systemMonitorRouter } from './api/system-monitor/system-monitor';
 import './api/music/sidecar-server'; // side-effect: capture the officer-music audio server port
 import { devServerRouter, devServerProxyRouter } from './api/dev-server/router';
 import { dockRouter } from './api/dock/dock';
@@ -93,6 +94,7 @@ protectedRouter.route('/dashboards', dashboardsRouter);
 protectedRouter.route('/task-logs', taskLogsRouter);
 protectedRouter.route('/file-browser', fileBrowserRouter);
 protectedRouter.route('/music', musicRouter);
+protectedRouter.route('/system-monitor', systemMonitorRouter);
 protectedRouter.route('/dev-server', devServerRouter);
 protectedRouter.route('/dock', dockRouter);
 protectedRouter.route('/integrations', integrationsRouter);