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/apps/officer-web/Screens/Dashboard/Layout/Dock.tsx

@@ -129,6 +129,7 @@ import {
   MonitorSmartphone,
   Workflow,
   Music,
+  Activity,
 } from 'lucide-react';
 
 export const ALL_DOCK_ITEMS: DockItem[] = [
@@ -145,6 +146,7 @@ export const ALL_DOCK_ITEMS: DockItem[] = [
   { label: 'Projects', to: '/projects', icon: FolderKanban, color: '#10b981' },
   { label: 'Browser', to: '/browser', icon: Globe, color: '#06b6d4' },
   { label: 'Desktop', to: '/desktop', icon: MonitorSmartphone, color: '#ec4899' },
+  { label: 'Monitor', to: '/system-monitor', icon: Activity, color: '#0ea5e9' },
   { label: 'Dashboards', to: '/dashboards', icon: LayoutGrid, color: '#8b5cf6' },
 ];