feat(dashboard): a curated default layout, merged duplicate widgets, a labelled Overview (#5213)

- New installs start from widgets.RECOMMENDED, packed row by row for the
  enabled plugins; the edit drawer can reset a dashboard to it.
- Host Agent — Resources folds into Hosts — Overview (which gains load 1m),
  UniFi — Devices into UniFi — Overview; migration 0032 moves existing
  dashboards onto the survivors.
- The Overview labels what it counts (hosts, monitors up/down/pending,
  alerts firing) and lists firing alerts and down monitors with since-times.
- Uptime polls every 5 minutes (poll_seconds) instead of every cycle.

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

plugins/unifi/templates/unifi/widget_devices.html

@@ -1,36 +0,0 @@
-{# unifi/widget_devices.html — dashboard widget: infrastructure devices #}
-{% if not devices %}
-<div style="color:var(--text-muted);font-size:0.85rem;padding:0.5rem 0;">
-  {% if type_filter != "all" %}No {{ type_filter }} devices found.{% else %}No devices found.{% endif %}
-</div>
-{% else %}
-
-{% set online = devices | selectattr("state", "equalto", 1) | list %}
-{% set offline = devices | rejectattr("state", "equalto", 1) | list %}
-
-<div style="display:flex;gap:1rem;margin-bottom:0.75rem;">
-  <div>
-    <span style="font-size:1.4rem;font-weight:500;line-height:1;color:var(--green);">{{ online | length }}</span>
-    <span style="font-size:0.78rem;color:var(--text-muted);margin-left:0.25rem;">online</span>
-  </div>
-  {% if offline %}
-  <div>
-    <span style="font-size:1.4rem;font-weight:500;line-height:1;color:var(--red);">{{ offline | length }}</span>
-    <span style="font-size:0.78rem;color:var(--text-muted);margin-left:0.25rem;">offline</span>
-  </div>
-  {% endif %}
-</div>
-
-<div style="display:grid;gap:3px;">
-  {% for d in devices %}
-  <div style="display:flex;align-items:center;gap:0.5rem;font-size:0.82rem;padding:0.15rem 0;">
-    <span class="dot {% if d.state == 1 %}dot-up{% else %}dot-down{% endif %}"></span>
-    <span style="flex:1;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;">
-      {{ d.name or d.mac }}
-    </span>
-    <span style="font-size:0.72rem;color:var(--text-dim);flex-shrink:0;">{{ d.model or d.device_type or "" }}</span>
-  </div>
-  {% endfor %}
-</div>
-
-{% endif %}