Add the Recent updates sheet behind the Home bell (Feature 21)

GET /api/v1/updates lists the last 10 distinct notification events from
the outbox, newest first and one per event key whatever its channels.
POST /api/v1/updates/seen {"through": created_at} moves
household_settings.updates_seen_at forward, so /api/v1/home's
recentUpdates.unread is true only for an event stored since. The Home
bell opens a Sheet listing the updates with relative times; a row opens
its URL, and opening the sheet marks the updates seen, clearing the
grape dot optimistically and putting it back if the mark fails.

Maestro task 96e2dc3f-1f8a-4114-bcb5-e0f93c349165.

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

migrations/queries/notifications.sql

@@ -74,3 +74,20 @@ SELECT EXISTS (
 	SELECT 1 FROM notification_outbox
 	WHERE CAST(sqlc.narg(since) AS TEXT) IS NULL OR created_at > CAST(sqlc.narg(since) AS TEXT)
 ) AS found;
+
+-- name: ListRecentNotifications :many
+-- Returns the last lim distinct events stored, newest first: one row per
+-- event key, the last stored for it whatever its channel, so an event
+-- stored for push and Google Chat is one row. The last, because a channel
+-- switched on later can store the same event key again, and
+-- HasNotificationSince counts that row: an event is as new as its newest
+-- row, so marking it seen also covers that row.
+SELECT o.event_key, o.payload, o.created_at FROM notification_outbox o
+WHERE o.id = (
+	SELECT i.id FROM notification_outbox i
+	WHERE i.event_key = o.event_key
+	ORDER BY i.created_at DESC, i.id DESC
+	LIMIT 1
+)
+ORDER BY o.created_at DESC, o.event_key DESC
+LIMIT sqlc.arg(lim);