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>

internal/db/settings.sql.go

@@ -161,6 +161,23 @@ func (q *Queries) GetRecipeSearchSettings(ctx context.Context) (RecipeSearchSett
 	return i, err
 }
 
+const markUpdatesSeen = `-- name: MarkUpdatesSeen :execrows
+UPDATE household_settings
+SET updates_seen_at = CAST(?1 AS TEXT)
+WHERE id = 1 AND (updates_seen_at IS NULL OR updates_seen_at < CAST(?1 AS TEXT))
+`
+
+// Moves updates_seen_at forward to seen_at; affects no row when it is
+// already at or after seen_at, so it never moves back. It is not a settings
+// edit: updated_by and updated_at are left as they are.
+func (q *Queries) MarkUpdatesSeen(ctx context.Context, seenAt string) (int64, error) {
+	result, err := q.db.ExecContext(ctx, markUpdatesSeen, seenAt)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected()
+}
+
 const recordChatTest = `-- name: RecordChatTest :execrows
 UPDATE chat_settings
 SET last_test_at = ?, last_test_status = ?, updated_at = ?