feat: Directory agent status + plugin modal rework, Vault restyle, navbar (v1.24.0)

- Merge theta-agent into Directory: remove the Agents page; add green/yellow/red
  status dots to host rows and a Metrics tab (telemetry + discovery) to the
  resource modal, joined to hosts by hostname, live via socket.io + 30s refresh.
- Discovery Plugins New-plugin modal: slug derived from name (field removed),
  cron dropdown (hourly/daily/weekly/custom), configSchema-driven settings
  (Proxmox url/tokenId/tokenSecret) sent as a populated config.
- Directory resource slug now read-only + derived from name.
- Vault page restyled to match the site.
- Navbar: username no longer underlined; only the active link is bold+underlined.
- docs/agents.md: document the Directory status/metrics + NAT troubleshooting.

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

nodejs/views/top.ejs

@@ -49,7 +49,7 @@
 				</ul>
 				<div class="form-inline mt-2 mt-md-0">
 					<% if(ui.profileUrl){ %>
-					<a id="cl-username" class="navbar-text text-light me-3" href="<%- ui.profileUrl %>" style="display: none;">
+					<a id="cl-username" class="navbar-text text-light me-3 text-decoration-none" href="<%- ui.profileUrl %>" style="display: none;">
 						<i class="fa-solid fa-user me-1"></i><span id="cl-username-text"></span>
 					</a>
 					<% } else { %>