feat(ui): alerts, monitors, hosts, schedules and maintenance lists put problems first, with since-times (#5210)

#5210 "Problems first, with since-time, across every list" (milestone 477),
first batch.

- Alerts: the Active list reads firing, no data, acknowledged, pending, the
  longest-running first, and re-polls itself. An acknowledged alert says how
  long it has been breaching (from the alert's events; acknowledging moves
  last_transition_at) and, apart from that, who acknowledged it and when.
  Rules show what each is doing now; disabled rules sort last. The current
  value reads the latest-value table (#5208) instead of plugin_metrics.
- Monitors: a down monitor says "Down 12m · connection refused" in the list.
- Hosts: sorted down, agent gone quiet, pending, healthy. The agent column
  shows "—" for a missing reading (was 0%) and a Stale badge with its age.
  agent_metrics_by_host is gone; the list reads agent_overview_by_host.
- Schedules: failing first (failed or interrupted run, or a firing that could
  not start one), then running, then the rest, paused last; status badge
  from the shared states.
- Maintenance windows: active (ending soonest), then upcoming (starting
  soonest), with expired folded away; each says when it ends/starts/ended.

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

steward/alerts/routes.py

@@ -7,7 +7,7 @@ from steward.auth.middleware import require_role
 from steward.alerts import service as alert_svc
 from steward.core.time_range import parse_range
 from steward.ansible import sources as src_module
-from steward.models.alerts import AlertRule, AlertOperator, MaintenanceWindow
+from steward.models.alerts import AlertRule, AlertOperator, AlertState, MaintenanceWindow
 from steward.models.users import UserRole
 
 alerts_bp = Blueprint("alerts", __name__, url_prefix="/alerts")
@@ -98,8 +98,23 @@ async def list_alerts():
     async with current_app.db_sessionmaker() as db:
         active = await alert_svc.active_rows(db, datetime.now(timezone.utc))
         rules = await alert_svc.list_rules(db)
+        states = {s.rule_id: s for s in (await db.execute(select(AlertState))).scalars()}
 
-    return await render_template("alerts/list.html", active=active, rules=rules, operators=_OPERATORS)
+    # Every rule with what it is doing now; disabled rules last.
+    rules.sort(key=lambda r: (not r.enabled, r.name.lower()))
+    rule_state = {r.id: alert_svc.alert_label(states[r.id]) for r in rules if r.id in states}
+    return await render_template(
+        "alerts/list.html", active=active, rules=rules, rule_state=rule_state,
+        operators=_OPERATORS, poll_interval=current_app.config.get("MONITORS_POLL_INTERVAL", 60))
+
+
+@alerts_bp.get("/active")
+@require_role(UserRole.viewer)
+async def active_fragment():
+    """The Active section alone, which the alerts page polls."""
+    async with current_app.db_sessionmaker() as db:
+        active = await alert_svc.active_rows(db, datetime.now(timezone.utc))
+    return await render_template("alerts/_active.html", active=active)
 
 
 HISTORY_LIMIT = 200
@@ -298,9 +313,14 @@ async def list_maintenance():
     now = datetime.now(timezone.utc)
     async with current_app.db_sessionmaker() as db:
         windows = await alert_svc.list_maintenance_windows(db)
+    # Active first (ending soonest first), then upcoming (starting soonest
+    # first); expired ones are history, newest first, folded away.
+    active = sorted((w for w in windows if w.start_at <= now <= w.end_at), key=lambda w: w.end_at)
+    upcoming = sorted((w for w in windows if w.start_at > now), key=lambda w: w.start_at)
+    expired = sorted((w for w in windows if w.end_at < now), key=lambda w: w.end_at, reverse=True)
     return await render_template(
         "alerts/maintenance.html",
-        windows=windows,
+        windows=windows, active=active, upcoming=upcoming, expired=expired,
         now=now,
         source_modules=alert_svc.source_modules(),
     )