fix(docker): collapse Swarm view per-cluster so multi-manager doesn't duplicate

Swarm services/nodes are cluster-global (every manager's API returns the same
list), but each manager reports them independently (rows keyed by host_id) and
the Swarm page grouped by reporting manager — so two managers in one cluster
listed every service and node twice.

Group the reporting managers into swarms in the swarm() view (managers sharing
any node_id are the same cluster, via union-find over node-set intersection),
then dedup within each: one service per name and one node per node_id, keeping
the freshest. Render one section per swarm ("reported by N managers · names").
node_id is globally unique so node dedup is always safe; grouping by node
overlap also keeps it correct if two separate swarms are ever monitored.

View-layer only — no schema/agent change. The main per-host container page is
unaffected (those are genuinely distinct per-node tasks).

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

plugins/docker/templates/docker/swarm.html

@@ -7,12 +7,14 @@
 
 <h1 class="page-title" style="margin-bottom:1.5rem;">Swarm</h1>
 
-{% if host_groups %}
-{% for g in host_groups %}
+{% if swarms %}
+{% for g in swarms %}
 <div style="margin-bottom:2rem;">
-  <div style="display:flex;align-items:baseline;gap:0.6rem;margin-bottom:0.75rem;">
-    <span style="font-weight:600;font-size:0.95rem;">{{ g.host_name }}</span>
-    <span style="font-size:0.78rem;color:var(--text-muted);">manager view</span>
+  <div style="display:flex;align-items:baseline;gap:0.6rem;margin-bottom:0.75rem;flex-wrap:wrap;">
+    <span style="font-weight:600;font-size:0.95rem;">Swarm</span>
+    <span style="font-size:0.78rem;color:var(--text-muted);">
+      reported by {{ g.managers | length }} manager{{ 's' if g.managers | length != 1 }} · {{ g.managers | join(", ") }}
+    </span>
   </div>
 
   {# ── Services ─────────────────────────────────────────────────────────── #}
@@ -39,7 +41,7 @@
           </td>
         </tr>
         {% else %}
-        <tr><td colspan="5" style="color:var(--text-muted);font-size:0.85rem;text-align:center;padding:1.5rem;">No services on this manager.</td></tr>
+        <tr><td colspan="5" style="color:var(--text-muted);font-size:0.85rem;text-align:center;padding:1.5rem;">No services in this swarm.</td></tr>
         {% endfor %}
       </tbody>
     </table>