feat: domain monitoring (merge plan M2, phase 1)

Port of the domain-intelligence pipeline from the old Beszel fork,
adapted to Dash's SQLite + no-PocketBase architecture:

- internal/domain: RDAP via IANA bootstrap (cached), TCP WHOIS :43
  fallback with multi-format parser, DNS (NS/MX/TXT/CNAME/A/AAAA),
  TLS leaf cert details, ip-api.com geolocation, provider detection
  (DNS/email/hosting/CA). HTML scraping, paid APIs, and exec-based
  whois deliberately dropped.
- API: domains CRUD + synchronous refresh + domain_checks snapshot
  history; refresh runs inside the monitor sweep on interval_h.
- UI: /domains + /domains/:id pages, add/edit dialog, domain board
  widget (favicon + expiry countdown), palette + nav entries,
  domainId picker in the widget dialog.
- Test seam: Server.lookup injects the refresh; domain tests run
  hermetic against a stubbed result.

Verified live: github.com resolves MarkMonitor expiry 2028-10,
Route 53 DNS, GitHub Pages hosting, Sectigo cert with 69d left.

Authored By: TDvorak <[email protected]>

Generated with Devin (https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/frontend/src/widgets/index.tsx

@@ -4,6 +4,7 @@ import { ClockWidget } from "@/widgets/clock";
 import { PiholeWidget, AdguardWidget } from "@/widgets/blocker";
 import { ImmichWidget } from "@/widgets/immich";
 import { MonitorWidget } from "@/widgets/monitor";
+import { DomainWidget } from "@/widgets/domain";
 
 // WidgetHost seam: renderers own the tile chrome; this maps config.type to
 // the component that fills it. Adding a widget = one fetcher in Go + one
@@ -30,6 +31,7 @@ const registry: WidgetRegistry = {
 	adguard: { view: AdguardWidget },
 	immich: { view: ImmichWidget },
 	monitor: { view: MonitorWidget },
+	domain: { view: DomainWidget },
 };
 
 export function cfgStr(item: Item, key: string): string {