feat(retention): every growing table is pruned; the audit log has its own window; charts read the raw window from Settings (#5155)

- prune_by_age(column) registers a time-series column with the hourly cleanup;
  Traefik (metrics, access summaries, global stats) and UniFi (WAN, client,
  WLAN, DPI, events, alarms, speedtests) register theirs in setup().
- Alert events join monitor results and Ansible runs on data.retention_days,
  read from Settings each run; Ansible run log files older than it are deleted.
- audit.retention_days (365) keeps the audit log longer, set on Settings > General.
- metric_series.points reads metrics.retention.raw_days, so the chart's
  raw/rollup seam is where the rollup put it (RAW_DAYS removed).

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

steward/settings/routes.py

@@ -101,7 +101,7 @@ async def save_general():
     form = await request.form
     whole: dict[str, int] = {}
     for key in ("session.lifetime_hours", "general.trusted_proxy_hops",
-                "login.max_failures", "login.lockout_minutes"):
+                "login.max_failures", "login.lockout_minutes", "audit.retention_days"):
         try:
             whole[key] = int(form.get(key, DEFAULTS[key]))
         except (TypeError, ValueError):