feat(traefik): each router problem says what it means, whether it's real, and what to do (#5712)

#5712 "Each router problem says what it means, whether it's real, and what
to do". A problem card now names its kind and reads its codes:
- Server errors: 500 means the app is failing; 502/503/504 means Traefik
  couldn't reach it or it timed out.
- Client errors: 404 scanners, a 401/403 login wall, 429 rate limiting, or
  499 clients giving up on a slow app.
- Slow: p95 against p50.
Each card says whether the problem is likely real, and ends with one next
step. A fault links to the swarm service behind the router, matched by
name, and traffic links to Settings → Thresholds. The wording lives in
plugins/traefik/meaning.py.

The plugin manager now hands out a loaded plugin's submodule
(loaded_plugin_submodule), so Traefik and host_agent reach Docker's
models the same way (#5775).

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

plugins/traefik/templates/traefik/rows.html

@@ -45,7 +45,7 @@
       {{ status_badge(r.state, "Failing" if r.state == 'crit' else "Warning") }}
       <h3 class="section-title" style="margin:0;word-break:break-all;">{{ r.name }}</h3>
     </div>
-    <p class="problem-detail" style="margin-bottom:0.5rem;">{{ r.why }}
+    <p class="problem-detail" style="margin-bottom:0.5rem;">{% if r.meaning %}<strong>{{ r.meaning.label }}</strong>: {% endif %}{{ r.why }}
       {%- if r.since_before %}, all of the last {{ current_range }}{% elif r.since %}, started {{ r.since|ago }}{% endif %}</p>
     {% if r.codes %}
     <p class="field-hint" style="margin:0 0 0.5rem;">Last 15 min:
@@ -56,6 +56,18 @@
     {% else %}
     <p class="field-hint" style="margin:0 0 0.5rem;">Status codes not recorded yet: Steward keeps them from this version on.</p>
     {% endif %}
+    {% if r.meaning %}
+    {# What it means and the one next step (#5712; plugins/traefik/meaning.py). #}
+    <p style="margin:0 0 0.3rem;font-size:0.85rem;">{{ r.meaning.meaning }} <span class="tone-muted">{{ r.meaning.likely }}</span></p>
+    <p class="field-hint" style="margin:0 0 0.5rem;">Next:
+      {%- if r.meaning.action == 'act' %}
+        {%- if r.service %} <a href="/plugins/docker/service/{{ r.service|urlencode }}">{{ r.service }}: its tasks and logs →</a>
+        {%- else %} look at the app's container and logs under <a href="/plugins/docker/swarm">Docker → Swarm</a>; Steward can't tell which service serves this router.
+        {%- endif %}
+      {%- else %} if this is normal for this router, raise the 4xx cutoff in <a href="/settings/thresholds/#traefik">Settings → Thresholds</a>. It is one cutoff for every router
+        {%- if not r.normed %}; once Steward has learned this router's normal for the hour, it flags only departures from it{% endif %}.
+      {%- endif %}</p>
+    {% endif %}
     <table class="table" style="font-size:0.85rem;">
         <tr><td class="field-hint">Req/s</td><td>{{ "%.2f"|format(r.latest.request_rate) }}</td><td>{{ r.sparkline_req|safe }}</td></tr>
         <tr><td class="field-hint">Bandwidth</td><td>{{ r.latest.response_bytes_rate|rate }}</td><td>{{ r.sparkline_bytes|safe }}</td></tr>