feat(dashboard): reference library + notification rule templates

- Built-in Reference page with plain-English documentation
- 13 topics: stream gauges, wildfire, FIRMS, weather, solar,
  ducting, avalanche, traffic, 511, mesh health, notifications,
  commands, API
- Searchable topic sidebar with anchor navigation
- Notification rule templates: 6 presets for quick setup
  - Mesh Health Monitoring
  - Weather & Fire Alerts
  - RF Conditions
  - Road & Traffic
  - Everything Critical
  - Morning Briefing
- All tables styled with dark theme and color indicators

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dashboard-frontend/src/components/Layout.tsx

@@ -7,6 +7,7 @@ import {
   Settings,
   Bell,
   BellRing,
+  BookOpen,
 } from 'lucide-react'
 import { fetchStatus, type SystemStatus } from '@/lib/api'
 import { useWebSocket } from '@/hooks/useWebSocket'
@@ -23,6 +24,7 @@ const navItems = [
   { path: '/config', label: 'Config', icon: Settings },
   { path: '/alerts', label: 'Alerts', icon: Bell },
   { path: '/notifications', label: 'Notifications', icon: BellRing },
+  { path: '/reference', label: 'Reference', icon: BookOpen },
 ]
 
 function formatUptime(seconds: number): string {