feat(panel): rename Account to Settings

The nav entry, page heading, and browser title now read Settings. The
route, template name, and Active key stay `account`, so existing links
and bookmarks keep working.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

internal/web/templates/layout.html

@@ -70,7 +70,7 @@
   {{template "sections" .}}
   <div class="session">
     <span class="muted">{{.User}}</span>
-    {{if eq .Active "account"}}<span aria-current="page">{{template "icon-account"}}Account</span>{{else}}<a href="/account">{{template "icon-account"}}Account</a>{{end}}
+    {{if eq .Active "account"}}<span aria-current="page">{{template "icon-account"}}Settings</span>{{else}}<a href="/account">{{template "icon-account"}}Settings</a>{{end}}
     <form class="inline" method="post" action="/logout">
       <button type="submit" class="danger">{{template "icon-sign-out"}}Sign out</button>
     </form>