feat: telemetry alert rules with webhook delivery

core.alert_rules (migration 00012) — heartbeat_silence and error_spike
rules evaluated by a 60s backend ticker. Transition-based firing:
alert.fired on breach, alert.resolved on recovery, both first-class
webhook event types riding the signed dispatcher + realtime stream.
Dashboard manages rules on the Integrations page.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/db/queries/alert_rules.sql

@@ -0,0 +1,49 @@
+-- name: CreateAlertRule :one
+INSERT INTO core.alert_rules (project_id, name, kind, config)
+VALUES ($1, $2, $3, $4)
+RETURNING *;
+
+-- name: ListAlertRules :many
+SELECT * FROM core.alert_rules
+WHERE project_id = $1
+ORDER BY name;
+
+-- name: ListEnabledAlertRules :many
+SELECT * FROM core.alert_rules
+WHERE enabled;
+
+-- name: GetAlertRule :one
+SELECT * FROM core.alert_rules
+WHERE id = $1 AND project_id = $2;
+
+-- name: UpdateAlertRule :one
+UPDATE core.alert_rules
+SET name = $3, config = $4, enabled = $5, updated_at = NOW()
+WHERE id = $1 AND project_id = $2
+RETURNING *;
+
+-- name: SetAlertRuleState :exec
+UPDATE core.alert_rules
+SET state = $3, updated_at = NOW()
+WHERE id = $1 AND project_id = $2;
+
+-- name: DeleteAlertRule :exec
+DELETE FROM core.alert_rules
+WHERE id = $1 AND project_id = $2;
+
+-- Per-component most recent heartbeat — heartbeat_silence detection.
+-- name: LastHeartbeats :many
+SELECT co.name AS component_name, max(e.ts)::timestamptz AS last_beat
+FROM core.components co
+JOIN core.events e ON e.component_id = co.id AND e.type = 'heartbeat'
+WHERE co.project_id = $1
+GROUP BY co.name;
+
+-- Per-component error count inside a sliding window — error_spike detection.
+-- name: RecentErrorCounts :many
+SELECT co.name AS component_name, count(*) AS errors
+FROM core.events e
+JOIN core.components co ON co.id = e.component_id
+WHERE e.project_id = $1 AND e.type = 'error'
+  AND e.ts > now() - make_interval(secs => $2::bigint)
+GROUP BY co.name;