feat(alerts): alert history page — transitions, deliveries, mutes and actions (#5066)

#5066 "Alert history page". /alerts/history lists every alert transition
in a range (1h–30d, the shared range picker), newest first, all rules or
one (?rule=). Each row: from → to, the value against the rule's condition
("no data" for a silent one), email and webhook sent or failed with the
error, "muted · <window>" (and "notified when the window ended") taken out
of the event note, other notes, and a link to the Ansible run an action
started. Range and rule changes swap only the rows (HTMX). Viewer role.

The Alerts page links each rule's history and the whole history. The query
moves to alert_svc.history, which MCP get_alert_history now uses too.

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

steward/alerts/service.py

@@ -12,7 +12,7 @@ from datetime import datetime, timezone
 from sqlalchemy import or_, select
 
 from steward.models.alerts import (
-    AlertOperator, AlertRule, AlertState, AlertStateEnum, MaintenanceWindow,
+    AlertEvent, AlertOperator, AlertRule, AlertState, AlertStateEnum, MaintenanceWindow,
 )
 from steward.models.metrics import PluginMetric
 from steward.models.monitors import MONITOR_TYPE_VALUES, Monitor
@@ -89,6 +89,21 @@ async def list_rules(db) -> list[AlertRule]:
     return list((await db.execute(select(AlertRule).order_by(AlertRule.name))).scalars())
 
 
+async def history(db, since: datetime, rule_id: str | None = None,
+                  limit: int = 200) -> list[tuple[AlertEvent, AlertRule]]:
+    """Alert transitions since `since`, newest first, with their rule; one
+    rule's when `rule_id` is given. Returns up to limit+1 rows so a caller can
+    tell the list was cut."""
+    stmt = (select(AlertEvent, AlertRule)
+            .join(AlertRule, AlertEvent.rule_id == AlertRule.id)
+            .where(AlertEvent.transitioned_at >= since)
+            .order_by(AlertEvent.transitioned_at.desc())
+            .limit(limit + 1))
+    if rule_id:
+        stmt = stmt.where(AlertEvent.rule_id == rule_id)
+    return [tuple(row) for row in (await db.execute(stmt)).all()]
+
+
 async def list_maintenance_windows(db) -> list[MaintenanceWindow]:
     """Every window, latest start first."""
     return list((await db.execute(