feat(docker): group containers by compose/swarm + enrich widget (milestone 77 #942)

Container list now sub-groups each host's containers by compose project (or
swarm service) with a small subheading, preserving the running-first order;
hosts with no such labels render flat as before. The dashboard status widget
links each container to its detail page and surfaces enriched state inline —
health dot (healthy/unhealthy), restart count, and last non-zero exit code for
stopped containers. Completes the #942 UI surface.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016Jg27rgypiW2efULXJDtMC

plugins/docker/templates/docker/rows.html

@@ -47,7 +47,11 @@
       </tr>
     </thead>
     <tbody>
-      {% for item in g.containers %}
+      {% for sub in g.subgroups %}
+      {% if g.grouped and sub.label %}
+      <tr><td colspan="7" style="padding:0.4rem 0.75rem 0.2rem;font-size:0.72rem;color:var(--text-dim);text-transform:uppercase;letter-spacing:0.05em;font-weight:600;">{{ sub.label }}</td></tr>
+      {% endif %}
+      {% for item in sub.containers %}
       {% set c = item.container %}
       <tr>
         <td>
@@ -105,6 +109,7 @@
         <td>{{ item.sparkline_mem | safe }}</td>
       </tr>
       {% endfor %}
+      {% endfor %}
     </tbody>
   </table>
 </div>