feat: monitors worker, auth register, scan polish

Add background DNS/SSL monitor checks, registration API, smoother SSE
with stage labels, improved CDN/WAF detection, light-theme UI polish,
and README roadmap updates.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/monitor-worker.ts

@@ -0,0 +1,27 @@
+/**
+ * Background monitor checks (DNS change + SSL expiry MVP).
+ * Run via: npm run worker:monitors
+ */
+import { runAllMonitorChecks } from "../src/lib/monitoring/check";
+
+const intervalMs = Number(process.env.MONITOR_INTERVAL_MS ?? 300_000);
+
+async function tick() {
+  const summary = await runAllMonitorChecks();
+  console.log(
+    `[monitor-worker] ${new Date().toISOString()} checked=${summary.checked} with_alerts=${summary.alerts}`
+  );
+}
+
+async function main() {
+  await tick();
+  setInterval(() => {
+    tick().catch((e) => console.error("[monitor-worker]", e));
+  }, intervalMs);
+  console.log(`[monitor-worker] interval ${intervalMs / 1000}s`);
+}
+
+main().catch((e) => {
+  console.error(e);
+  process.exit(1);
+});