fix(db): add LIMIT to unbounded queries causing OOMKill

- Add LIMIT 10000 to fetchSeasonSnapshots (season_snapshots per season)
- Add LIMIT 500 to fetchChampionshipBracket (series per season bracket)

These queries were called in a loop for each season without LIMITs,
causing acb-index-builder to be OOMKilled with 512Mi memory limit.

Fixes OOMKill after web asset copy in build cycle.

cmd/acb-index-builder/db.go

@@ -645,6 +645,7 @@ func fetchSeasonSnapshots(ctx context.Context, db *sql.DB, seasonID int64) ([]Se
 		JOIN bots b ON ss.bot_id = b.bot_id
 		WHERE ss.season_id = $1
 		ORDER BY ss.rank
+		LIMIT 10000
 	`, seasonID)
 	if err != nil {
 		return nil, err
@@ -679,6 +680,7 @@ func fetchChampionshipBracket(ctx context.Context, db *sql.DB, seasonID int64) (
 		        WHEN 'final' THEN 2
 		    END,
 		    s.bracket_position
+		LIMIT 500
 	`, seasonID)
 	if err != nil {
 		return nil, err