perf: reduce trending refresh load

[raymondjacobson]

Summary

• add a replacement partial genre index for the live TRACKS/pnagD score slice, then drop redundant/broad track_trending_scores indexes that add refresh write amplification
• change TrendingJob scheduling so a slow run waits the full interval before the next run instead of consuming a pending ticker event immediately
• split allTime track score refresh from the hourly week/month pass and gate it with a 24-hour indexing_checkpoints checkpoint

Test

• go test ./jobs -run TestTrendingJob -count=1
• go test ./jobs
• go test ./jobs ./indexer
• applied ddl/migrations/0225_track_trending_scores_index_cleanup.sql successfully against a throwaway local DB cloned from test_jobs