Shares of other services and RepoISO integration

- include SMB drop-ins from /etc/samba/smb.conf.d into the generated smb.conf
- keep smbd/nfs-server running while other services (/etc/exports.d, drop-ins) share,
  instead of disabling them when nasmon has no shares of its own
- list those shares read-only on /shares
- settings: RepoISO URL; poll its /api/integration/status, dashboard card, menu link,
  alerts for portal down, stale worker, failed jobs, unmounted publications

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/templates/settings.html

@@ -67,6 +67,17 @@
   <p class="muted small">Tests start only for disks that are awake. A long test on a large HDD takes many hours; disk stays usable.</p>
 </section>
 
+<section class="card">
+  <h2>Integrations</h2>
+  <div class="form-grid">
+    <label class="wide">RepoISO URL <input name="repoiso_url" value="{{$c.Integrations.RepoISOURL}}" placeholder="http://127.0.0.1"></label>
+  </div>
+  <p class="muted small">RepoISO (ISO library, apt/dnf repositories, Proxmox ISO exports) on this host. nasmon polls
+    <span class="mono">&lt;url&gt;/api/integration/status</span> every minute, shows a dashboard card, alerts when the portal
+    or its worker is down, and adds a menu link. Use the local address (<span class="mono">http://127.0.0.1</span>) — the
+    status endpoint only answers on loopback. Empty disables the integration.</p>
+</section>
+
 <div class="actions">
   <button type="submit" name="action" value="save">Save</button>
   <button type="submit" name="action" value="test" class="secondary">Save &amp; send test e-mail</button>