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/static/chart-colors.js

@@ -0,0 +1,23 @@
+// Design tokens as colours a <canvas> can paint with. A chart is drawn on a
+// canvas, which can't read var(--green), so each token is resolved through a
+// hidden element to the rgb() the browser computed for it.
+//
+// Loaded after the stylesheets (a script waits for the sheets above it), so the
+// tokens are defined by the time this runs. It also gives every Chart.js chart
+// the page's text and grid colours, so a chart config only names its series.
+(function () {
+  function stewardColor(name) {
+    var probe = document.createElement('span');
+    probe.style.display = 'none';
+    probe.style.color = 'var(' + name + ')';
+    document.documentElement.appendChild(probe);
+    var value = getComputedStyle(probe).color;
+    probe.remove();
+    return value;
+  }
+  window.stewardColor = stewardColor;
+  if (window.Chart) {
+    Chart.defaults.color = stewardColor('--text-muted');
+    Chart.defaults.borderColor = stewardColor('--border');
+  }
+})();

steward/static/steward.css

@@ -86,8 +86,8 @@ code { font-family: var(--fs-font-mono); font-size: 0.875em; background: var(--b
   color: var(--gold); border-left-color: var(--gold);
   background: color-mix(in srgb, var(--gold) 8%, transparent);
 }
-/* How many alerts need attention, beside the Alerts link. */
-.nav-count {
+/* A small count that needs attention: alerts beside the Alerts link, UniFi alarms. */
+.count-badge {
   margin-left: auto; padding: 0 0.45em; border-radius: var(--fs-radius-sm);
   background: var(--red-dim); color: var(--red); font-size: 0.75rem; font-weight: 500;
   font-variant-numeric: tabular-nums;