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/templates/layout.html

@@ -13,14 +13,22 @@
   {{if .LoggedIn}}
   <nav>
     <a href="/">Overview</a>
-    <a href="/network">Network</a>
-    <a href="/dhcp">DHCP</a>
-    <a href="/dns">DNS</a>
-    <a href="/wireguard">WireGuard</a>
-    <a href="/firewall">Firewall</a>
-    <a href="/ddns">Dynamic DNS</a>
-    <a href="/update">Update</a>
-    <a href="/advanced">Advanced</a>
+    <details name="menu"><summary>Network</summary><div>
+      <a href="/network">Interfaces</a>
+      <a href="/dhcp">DHCP</a>
+      <a href="/dns">DNS</a>
+      <a href="/wireguard">WireGuard</a>
+      <a href="/firewall">Firewall</a>
+    </div></details>
+    <details name="menu"><summary>Services</summary><div>
+      <a href="/ddns">Dynamic DNS</a>
+      <a href="/dnsproviders">DNS providers</a>
+      <a href="/certificate">Certificate</a>
+    </div></details>
+    <details name="menu"><summary>System</summary><div>
+      <a href="/update">Update</a>
+      <a href="/advanced">Advanced</a>
+    </div></details>
     <form method="post" action="/logout"><input type="hidden" name="csrf" value="{{.CSRF}}"><button class="link">Log out</button></form>
   </nav>
   {{end}}
@@ -31,5 +39,6 @@
   {{if .Error}}<p class="error">{{.Error}}</p>{{end}}
   {{template "content" .}}
 </main>
+<script src="/static/menu.js"></script>
 </body>
 </html>