fix(docker): use /api/monitoring/health for healthcheck (#296)

The healthcheck script was querying /api/settings which returns config
data rather than system health. Updated to /api/monitoring/health which
is the canonical health endpoint used across tests, SystemMonitor.tsx,
MaintenanceBanner.tsx, playwright config, and MCP tools.

scripts/healthcheck.mjs

@@ -2,12 +2,12 @@
 
 /**
  * Docker healthcheck script for OmniRoute.
- * Checks the /api/settings endpoint on the dashboard port.
+ * Checks the /api/monitoring/health endpoint on the dashboard port.
  * Used by Dockerfile and docker-compose files.
  */
 const port = process.env.DASHBOARD_PORT || process.env.PORT || "20128";
 
-fetch(`http://127.0.0.1:${port}/api/settings`)
+fetch(`http://127.0.0.1:${port}/api/monitoring/health`)
   .then((r) => {
     if (!r.ok) throw new Error(`HTTP ${r.status}`);
   })