fix: BUG-33 CPU threshold, TASK-27 tab icons, TASK-36 iframe errors

- BUG-33: CPU load alert threshold increased from 2x to 4x core count
  (8→16 on 4-core machine) to reduce false alerts during container ops
- TASK-27: Launch buttons for new-tab apps now show external link icon
  (BTCPay, Grafana, PhotoPrism, Portainer, OnlyOffice, etc.)
- TASK-36: Iframe error screen now distinguishes between X-Frame-Options
  blocked vs container not reachable, with appropriate messaging

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/src/stores/appLauncher.ts

@@ -54,6 +54,7 @@ const PORT_TO_APP_ID: Record<string, string> = {
   '18081': 'nostr-rs-relay',
   '7777': 'indeedhub',
   '50002': 'electrumx',
+  '3010': 'thunderhub',
 }