Add HTTP method/body, alert escalation, baseline alerts, notification grouping, rate limiting, App.js split, and API tests

- HTTP method + request body: GET/POST/PUT/PATCH/DELETE/HEAD selector and body textarea for http/health checks; stored in http_method/http_body columns; monitorService sends correct axios method+data
- Alert escalation: incidents open longer than escalation_hours get forwarded to fallback_webhook and marked escalated=1; hourly cron in scheduler
- Baseline-relative slow alerts: effectiveThreshold = response_time_threshold || (baseline * 2) — adaptive threshold without manual config
- Notification grouping: pendingAlerts collected per check cycle; ≥2 alerts flush as one grouped email+webhook; individual in-app entries still saved per resource
- Rate limiting: in-memory per-IP limiter (20/min heartbeat, 60/min status-page); no external package
- App.js split: Dashboard.js (monitors list + modals) and ResourceDetail.js extracted; App.js reduced from ~1987 to ~80 lines
- formatDuration moved to utils/timeUtils.js; imported by both new components
- DB migrations: http_method, http_body, incidents.escalated columns
- 18 passing API/unit tests (node:test, zero dependencies)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/src/utils/timeUtils.js

@@ -112,10 +112,19 @@ export const getTimezoneInfo = () => {
   const tz = getCurrentTimezone();
   const now = new Date();
   const tzDisplay = now.toLocaleTimeString('en-US', { timeZoneName: 'short' }).split(' ').pop();
-  
+
   return {
     timezone: tz,
     abbreviation: tzDisplay,
     offset: now.getTimezoneOffset()
   };
-};
+};
+
+export function formatDuration(ms) {
+  if (!ms || ms < 0) return '0m';
+  const minutes = Math.floor(ms / 60000);
+  const hours = Math.floor(minutes / 60);
+  const mins = minutes % 60;
+  if (hours > 0) return `${hours}h ${mins}m`;
+  return `${mins}m`;
+}