feat(settings): Settings brought into line with the rest of Steward (milestone 493)

The last page of #5214's walk. Settings still described Steward as it was
before monitors were unified and SNMP was rebuilt, drew its tabs below the
breadcrumb, and showed the report schedule in UTC.

- Tabs (#5377): settings/_tabs.html is a settings_tabs() macro called in
  each page's section_tabs block, above the trail, as Ansible's are. The
  breadcrumb guard also fails any page that {% include %}s a tab strip.
- Report time (#5378): reports.schedule_tz keeps the zone of whoever saved
  the schedule; check_and_send compares in it (report_due), and the form shows
  the day and hour on the reader's clock (schedule_in) under their zone's
  name. "Last sent" uses |when.
- Wording (#5379): the report contents list what the report holds (monitors,
  not ping-enabled hosts); "Ping latency" is "Response time" and says what it
  grades; plugin detail says enabling loads now and disabling needs a
  restart; the monitor interval says it applies on the next check (the
  scheduler reads it every pass); the dead list-config branch is gone.
- Traefik (#5380): the 5xx and 4xx cutoffs are settings
  (traefik.threshold.error_5xx_pct 0.1, error_4xx_pct 1.0) in a "Traefik
  routers" group on Thresholds while the plugin runs, read by router_state
  through error_cutoffs(). The Traefik page has a Thresholds button for
  admins, to /settings/thresholds/#traefik.

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

steward/templates/settings/plugin_detail.html

@@ -2,10 +2,10 @@
 {% extends "base.html" %}
 {% from "_macros.html" import crumbs %}
 {% block title %}{{ plugin.get('name', plugin._dir) }} Settings — Steward{% endblock %}
+{% from "settings/_tabs.html" import settings_tabs %}
+{% block section_tabs %}{{ settings_tabs("plugins") }}{% endblock %}
 {% block breadcrumb %}{{ crumbs([("Settings", "/settings/"), ("Plugins", "/settings/plugins/"), (plugin.get('name', plugin._dir), "")]) }}{% endblock %}
 {% block content %}
-{% set active_tab = "plugins" %}
-{% include "settings/_tabs.html" %}
 
 <div style="display:flex;align-items:center;gap:1rem;margin-bottom:1.5rem;">
   <h1 class="page-title" style="margin-bottom:0;">{{ plugin.get('name', plugin._dir) }}</h1>
@@ -18,7 +18,7 @@
                  background:color-mix(in srgb,var(--green) 12%,var(--bg));color:var(--green);">Loaded</span>
   {% elif plugin._enabled %}
     <span style="font-size:0.75rem;padding:0.15em 0.55em;border-radius:3px;
-                 background:var(--bg-elevated);color:var(--text-muted);">Enabled (restart required)</span>
+                 background:var(--bg-elevated);color:var(--text-muted);">Enabled, not loaded</span>
   {% else %}
     <span style="font-size:0.75rem;padding:0.15em 0.55em;border-radius:3px;
                  background:var(--bg-elevated);color:var(--text-muted);">Disabled</span>
@@ -55,7 +55,7 @@
       </label>
     </div>
     <div style="font-size:0.8rem;color:var(--text-muted);margin-top:0.4rem;margin-left:1.6rem;">
-      Enable/disable changes take effect after a restart.
+      Enabling loads the plugin straight away. Disabling takes effect after a restart.
     </div>
   </div>
 
@@ -67,16 +67,7 @@
 
       {% for cfg_key, cfg_default in plugin.config.items() %}
 
-        {% if cfg_default is iterable and cfg_default is not string and cfg_default is not mapping %}
-          <div style="display:flex;align-items:flex-start;gap:0.5rem;padding:0.5rem 0.75rem;
-                      background:var(--bg);border-radius:5px;border:1px solid var(--border);
-                      font-size:0.82rem;color:var(--text-muted);">
-            <span style="flex-shrink:0;">📋</span>
-            <span><strong style="color:var(--text);">{{ field_label(cfg_key) }}</strong> — list config, edit in
-              <code>plugin.yaml</code> ({{ cfg_default | length }} item{{ 's' if cfg_default | length != 1 }}).</span>
-          </div>
-
-        {% elif cfg_default is mapping %}
+        {% if cfg_default is mapping %}
           <div style="padding:0.75rem;background:var(--bg);border-radius:5px;border:1px solid var(--border);">
             <div style="font-size:0.74rem;color:var(--text-muted);text-transform:uppercase;
                         letter-spacing:0.05em;margin-bottom:0.6rem;">{{ field_label(cfg_key) }}</div>