Add DNS accounts, Let's Encrypt, password change, reboot, HTTP redirect

- router.dnsProviders: named accounts at DNS providers, used by dynamic
  DNS and certificates (ddclient and lego provider lists in
  pkgs/router-webui/providers.json). Schema 2 migrates router.ddns.
- router.acme: a Let's Encrypt certificate for the web UI via
  security.acme (DNS-01, resolver 1.1.1.1), served and reloaded by the
  web UI; Certificate page.
- Web UI: password change (web UI and root), reboot button, HTTP to HTTPS
  redirect (router.webui.httpPort), grouped menu.
- Latest kernel (linuxPackages_latest); 7.3 and 7.3.0 are the same kernel
  for the reboot hint.
- SPECS.md: wanted later (REST API, GraphQL, MCP).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeFqV9dZrK6nipHkPfyM4F

pkgs/router-webui/static/menu.js

@@ -0,0 +1,13 @@
+// Menus close on a click elsewhere; forms with data-confirm ask first.
+// Close an open menu when the click is somewhere else.
+document.addEventListener("click", function (e) {
+  document.querySelectorAll("nav details[open]").forEach(function (d) {
+    if (!d.contains(e.target)) d.removeAttribute("open");
+  });
+});
+
+// Ask before a form marked data-confirm is sent.
+document.addEventListener("submit", function (e) {
+  var q = e.target.getAttribute("data-confirm");
+  if (q && !confirm(q)) e.preventDefault();
+});

pkgs/router-webui/static/style.css

@@ -7,6 +7,12 @@ body { margin: 0; font: 15px/1.5 system-ui, sans-serif; color: var(--fg); backgr
 header { display: flex; gap: 1.5rem; align-items: center; padding: .75rem 1rem; border-bottom: 1px solid var(--line); flex-wrap: wrap; }
 nav { display: flex; gap: 1rem; align-items: center; flex-wrap: wrap; }
 nav form { display: inline; }
+nav details { position: relative; }
+nav summary { cursor: pointer; color: var(--accent); list-style: none; }
+nav summary::-webkit-details-marker { display: none; }
+nav summary::after { content: " \25BE"; }
+nav details > div { position: absolute; z-index: 10; top: 1.6rem; left: -.75rem; min-width: 11rem; display: flex; flex-direction: column; gap: .35rem;
+  padding: .6rem .75rem; background: var(--bg); border: 1px solid var(--line); border-radius: 6px; box-shadow: 0 4px 12px rgba(0, 0, 0, .15); }
 a { color: var(--accent); }
 main { max-width: 72rem; margin: 0 auto; padding: 1rem; }
 h1 { font-size: 1.4rem; margin: .5rem 0 1rem; }