Remove the RepoISO integration; keep generic support for shares of other services

RepoISO now manages the NAS itself, so nasmon no longer polls it (settings field, dashboard card,
menu link and repoiso:* alerts are gone). Drop-in SMB includes, read-only listing and keeping
smbd/nfs-server running for other software's shares stay.

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

internal/web/templates/shares.html

@@ -152,7 +152,7 @@
     <tbody>
     {{range .External}}<tr>
       <td><span class="badge">{{if eq .Kind "smb"}}SMB{{else}}NFS{{end}}</span></td>
-      <td>{{if eq .Source "repoiso"}}{{if $.RepoISO}}<a href="{{$.RepoISO}}/proxmox" target="_blank" rel="noopener">RepoISO</a>{{else}}RepoISO{{end}}{{else}}{{.Source}}{{end}}</td>
+      <td class="mono">{{.Source}}</td>
       <td class="mono">{{if .Name}}\\{{$.Data.Host}}\{{.Name}}{{else}}—{{end}}</td>
       <td class="mono small">{{.Path}}</td>
       <td class="mono small">{{.Clients}}</td>