fix(db): add LIMIT to fetchSeriesGames query to prevent OOMKill

The fetchSeriesGames function was querying all games for a series without a limit.
With up to 1000 series being fetched, and potentially many games per series,
this could return an unbounded number of rows and cause OOMKill.

A typical series has 3-7 games (best-of-5 or best-of-7), so LIMIT 100 is
more than sufficient to handle edge cases while preventing memory exhaustion.

Fixes acb-index-builder CrashLoopBackOff caused by OOMKill after web asset copy.

cmd/acb-index-builder/db.go

@@ -522,6 +522,7 @@ func fetchSeriesGames(ctx context.Context, db *sql.DB, seriesID int64) ([]Series
 		LEFT JOIN matches m ON sg.match_id = m.match_id
 		WHERE sg.series_id = $1
 		ORDER BY sg.game_num
+		LIMIT 100
 	`, seriesID)
 	if err != nil {
 		return nil, err