feat(plugins): Traefik problems first, UniFi/SNMP/fleet on shared shapes, audit names its entities, templates on tokens (#5126)

Traefik: routers are graded from their latest scrape (router_state: crit on
any real 5xx share, warn on p95 past the latency critical cutoff or a high
4xx share). Failing and slow routers lead as cards that say why; healthy
ones fold into one table that stays open or shut across polls. Proxy
counts are stat tiles; certificates are graded by Settings -> Thresholds
(tls_days).

UniFi: WAN health is a stat strip (latency graded by the thresholds),
devices carry status dots, event categories and firewall actions are
badges, the alarm count reuses .count-badge (renamed from .nav-count).
SNMP: each device wears a status badge and its readings are stat tiles.

Agent fleet: the table comes first, with a Status column (Reporting /
Silent / Never reported, by the host page's stale_after_seconds), silent
agents first, hosts linked, last seen as |ago.

Audit: entries name their entity (one query per type, steward/audit/
service.py) and link it; something deleted since keeps the name its entry
recorded and says "(deleted)".

Tokens: charts read colours through chart-colors.js (stewardColor resolves
a token to the rgb the browser computed; Chart.js defaults take the page's
text and border colours), so host, history, Traefik and SNMP charts drop
their hex. Template hex colours reach 0 (HEX_CEILING = 0), the last rgba
pills go, and heavy weights (600/700/bold, 60 of them) become 500, the
house pair being 400/500; a guard keeps templates there.

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

steward/templates/base.html

@@ -25,6 +25,7 @@
     <link rel="stylesheet" href="{{ url_for('static', filename='fonts/fonts.css') }}">
     <link rel="stylesheet" href="{{ url_for('static', filename='theme.css') }}">
     <link rel="stylesheet" href="{{ url_for('static', filename='steward.css') }}">
+    <script src="{{ url_for('static', filename='chart-colors.js') }}"></script>
     {% block head %}{% endblock %}
 </head>
 <body>
@@ -62,7 +63,7 @@
       <div class="nav-group">
         <div class="nav-group-label">Monitoring</div>
         <a href="/monitors/" {% if _p.startswith('/monitors') %}class="active" aria-current="page"{% endif %}>Monitors</a>
-        <a href="/alerts/" {% if _p.startswith('/alerts') %}class="active" aria-current="page"{% endif %}>Alerts{% if active_alert_count %} <span class="nav-count" title="{{ active_alert_count }} alert{{ 's' if active_alert_count != 1 }} need{{ 's' if active_alert_count == 1 }} attention">{{ active_alert_count }}</span>{% endif %}</a>
+        <a href="/alerts/" {% if _p.startswith('/alerts') %}class="active" aria-current="page"{% endif %}>Alerts{% if active_alert_count %} <span class="count-badge" title="{{ active_alert_count }} alert{{ 's' if active_alert_count != 1 }} need{{ 's' if active_alert_count == 1 }} attention">{{ active_alert_count }}</span>{% endif %}</a>
       </div>
       <div class="nav-group">
         <div class="nav-group-label">Automation</div>