feat(jobs): port 5 celery beat tasks from discovery-provider

[raymondjacobson]

Summary

Ports 5 periodic celery tasks from `apps/packages/discovery-provider` into the existing `api/jobs/` framework. Each job is its own file, follows the `Run` + `ScheduleEvery` + mutex-guarded `isRunning` pattern (matching `record_balance_history.go` / `reclaim_rent.go`), and is scheduled inside `CoreIndexer.Start` next to the existing aggregates calculator.

These fill gaps left after the discovery → go-openaudio cutover. Tables they read/write already exist in api/'s schema (verified against `sql/01_schema.sql`).

Jobs

File	Interval	Purpose
`index_hourly_play_counts.go`	30s	Bucket new plays into `hourly_play_counts`. Powers `GET /v1/metrics/plays`.
`prune_plays.go`	30s	DELETE plays older than ~400 days, 50k/run cap.
`index_user_listening_history.go`	5s	Merge new plays into per-user `listening_history` JSONB (cap 1000 tracks/user).
`index_trending.go`	10s	Score-only port. Refresh `aggregate_interval_plays` + `trending_params` MVs, then run pnagD + AnlGe trending strategy SQL templates verbatim into `track_trending_scores` + `playlist_trending_scores`.
`update_delist_statuses.go`	5min	Poll `notifier.audius.co/statuses/{users,tracks}` with delegate-signed Authorization header, apply delists to `users.is_available` / `tracks.is_available` + `is_delete` / `is_deactivated`, advance `delist_status_cursor`.

Plus `delegate_auth.go`: `signedHTTPGet` helper porting apps' `basic_auth_nonce` (ETH personal-sign over keccak'd timestamp, base64'd `Basic :<sig_hex>` header).

Scoping decisions

1. Trending: score-only. apps' `index_trending.py` also writes trending-mover notifications and calls `index_tastemaker` which dispatches challenge events. Both depend on the challenges/notification systems that aren't ported yet. The scoring half is what makes `/v1/tracks/trending`, `/v1/playlists/trending`, `/v1/tracks/trending/underground` non-empty — that's the user-facing parity.

2. Trusted notifier hardcoded to `https://notifier.audius.co/\`. apps reads from config; we don't need multi-notifier support today. Easy promotion to a config knob later if needed.

3. No new config required. `config.Cfg.DelegatePrivateKey` already exists.

Wiring

// indexer/indexer.go — CoreIndexer.Start
ci.startParityJobs(ctx)

`startParityJobs` instantiates each job with `ci.Config` and `ci.pool` and calls `ScheduleEvery`. Each job self-manages its goroutine and exits on `ctx.Done()` — they don't join the errgroup since they're best-effort background work.

Test plan

• `go build ./...` clean
• `go vet ./jobs/ ./indexer/` clean
• `go test ./jobs/` passes against `test_jobs` template DB (api-db-1)
• `TestHourlyPlayCountsJob_FullPipeline` — buckets, checkpoints, idempotent re-runs.
• `TestHourlyPlayCountsJob_NoPlays` — no-op on empty plays table.
• `TestPrunePlaysJob_DeletesOnlyOld` — recent plays survive, old ones go.
• `TestPrunePlaysJob_RespectsBatchSize` — per-run cap honored.
• `TestUserListeningHistoryJob_InsertsFirstHistory` — first batch sorts + counts correctly.
• `TestUserListeningHistoryJob_MergesAcrossRuns` — `play_count` sums across batches.
• `TestMergeListeningHistory_CapsToLimit` — JSONB capped to limit.
• `TestTrendingJob_PopulatesScores` — scores land + DELETE-then-INSERT means no dupes on rerun.
• `TestBasicAuthNonce_Shape` — Authorization header decodes to expected `:<sig_hex>` format.

Out of scope (called out in the parity discussion)

• `update_aggregates` — separate job in `aggregates_calculator.go` already exists.
• `index_aggregate_tips`, `index_metrics`, `index_profile_challenge_backfill` — explicitly skipped.
• `index_challenges` — bigger effort, separate PR.
• Trending notifications + tastemaker challenges — lands with the challenges work.

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