feat(docker): container log viewer + Settings controls [M79 step 5]

The user-facing half (rule 27). Per-container log viewer + admin controls, so
container logs are something the operator can actually touch.

Viewer (plugins/docker):
- /container/<host>/<name>/logs full page + /logs/lines HTMX fragment polled
  every 5s (near-live follow); stream filter (all/stdout/stderr) + case-insensitive
  text search; newest-first so the latest lines survive the poll's scroll reset;
  empty/loading states; a "View logs" link from the container detail page.
  Jinja auto-escapes log content (no markup injection).

Settings (Thresholds & Retention tab):
- global on/off toggle, comma-separated exclude list, retention days + max MB
  per container — DB-backed, no restart. The toggle + exclude are enforced
  authoritatively at ingest (_persist_logs drops disabled/excluded lines), since
  the push model has no channel to tell an agent to stop.

Tests: route-defined smoke; template-parse covers the new templates; integration
test for the ingest-time toggle + exclude enforcement.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CAGR73DUowdVFVvYzLXC5C

plugins/docker/templates/docker/container_logs.html

@@ -0,0 +1,51 @@
+{# docker/container_logs.html — per-container log viewer (m79) #}
+{% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
+{% block title %}Logs — {{ name }} — Docker — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([
+  ("Docker", "/plugins/docker/"),
+  (name, "/plugins/docker/container/" ~ host_id ~ "/" ~ name),
+  ("Logs", "")]) }}{% endblock %}
+{% block content %}
+
+<div style="display:flex;align-items:baseline;gap:0.6rem;margin-bottom:0.35rem;flex-wrap:wrap;">
+  <h1 class="page-title" style="margin-bottom:0;">{{ name }}</h1>
+  <span style="font-size:0.9rem;color:var(--text-muted);">logs</span>
+</div>
+<div style="font-size:0.82rem;color:var(--text-muted);margin-bottom:1rem;">
+  Recent lines (newest first) collected by the host agent{% if host %} on
+  <a href="/hosts/{{ host.id }}" style="color:var(--text-muted);">{{ host.name }}</a>{% endif %} —
+  updated every few seconds.
+  <a href="/plugins/docker/container/{{ host_id }}/{{ name }}">← back to container</a>
+</div>
+
+{# ── Controls: stream filter + text search (drive the fragment via HTMX) ───── #}
+<form id="log-controls" onsubmit="return false;"
+      style="display:flex;gap:0.6rem;align-items:center;flex-wrap:wrap;margin-bottom:0.6rem;">
+  <label style="font-size:0.8rem;color:var(--text-muted);display:flex;align-items:center;gap:0.35rem;">
+    Stream
+    <select name="stream" style="padding:0.25rem 0.4rem;">
+      <option value="all">all</option>
+      <option value="stdout">stdout</option>
+      <option value="stderr">stderr</option>
+    </select>
+  </label>
+  <input type="search" name="q" placeholder="Filter lines…" autocomplete="off"
+         aria-label="Filter log lines"
+         style="flex:1;min-width:180px;padding:0.3rem 0.5rem;">
+</form>
+
+<div class="card-flush">
+  <div id="log-lines"
+       hx-get="/plugins/docker/container/{{ host_id }}/{{ name }}/logs/lines"
+       hx-trigger="load, every 5s, change from:#log-controls, keyup changed delay:400ms from:#log-controls"
+       hx-include="#log-controls"
+       hx-swap="innerHTML"
+       role="log" aria-live="polite" tabindex="0"
+       style="max-height:70vh;overflow:auto;padding:0.5rem 0.75rem;
+              font-family:ui-monospace,monospace;font-size:0.8rem;line-height:1.5;">
+    <div style="color:var(--text-muted);">Loading…</div>
+  </div>
+</div>
+
+{% endblock %}