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

tests/plugins/docker/test_routes.py

@@ -35,6 +35,12 @@ def test_disk_prune_view_defined():
     assert callable(r.disk_prune)
 
 
+def test_container_log_views_defined():
+    # M79 per-container log viewer + its HTMX-polled line fragment.
+    assert callable(r.container_logs)
+    assert callable(r.container_logs_lines)
+
+
 def test_prune_extra_vars_mapping():
     """The prune buttons drive one playbook via prune_target; only 'images'
     widens to ALL unused images (docker image prune -a), system stays -f."""