LAN opt-in, mDNS migration, security hardening, path-based routing

- LAN discovery disabled by default (opt-in via [lan] enabled = true)
- Replace custom JSON multicast (239.255.70.78:5390) with standard mDNS
  (_numa._tcp.local on 224.0.0.251:5353) using existing DNS parser
- Instance ID in TXT record for multi-instance self-filtering
- API and proxy bind to 127.0.0.1 by default (0.0.0.0 when LAN enabled)
- Path-based routing: longest prefix match with optional prefix stripping
  via [[services]] routes = [{path, port, strip?}]
- REST API: GET/POST/DELETE /services/{name}/routes
- Dashboard shows route lines per service when configured
- Segment-boundary route matching (prevents /api matching /apiary)
- Route path validation (rejects path traversal)

Closes #11

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

site/dashboard.html

@@ -1098,12 +1098,20 @@ function renderServices(entries) {
         ? '<span class="lan-badge shared" title="Reachable from other devices on the network">LAN</span>'
         : '<span class="lan-badge local-only" title="Bound to localhost — not reachable from other devices. Start with 0.0.0.0 to share on LAN.">local only</span>')
       : '';
+    const routeLines = (e.routes || []).map(r =>
+      `<div class="service-port" style="color:var(--text-dim);">` +
+        `<span style="display:inline-block;min-width:60px;">${r.path}</span> ` +
+        `&rarr; :${r.port}` +
+        (r.strip ? ` <span style="opacity:0.6;">(strip)</span>` : '') +
+      `</div>`
+    ).join('');
     return `
     <div class="service-item">
       <span class="health-dot ${e.healthy ? 'up' : 'down'}" title="${e.healthy ? 'running' : 'not reachable'}"></span>
       <div class="service-info">
         <div class="service-name"><a href="${e.url}" target="_blank">${e.name}.numa</a>${lanBadge}</div>
         <div class="service-port">localhost:${e.target_port} &rarr; proxied</div>
+        ${routeLines}
       </div>
       ${e.name === 'numa' ? '' : `<button class="btn-delete" onclick="deleteService('${e.name}')" title="Remove service">&times;</button>`}
     </div>