perf(playout): parallelize playlist validation with dedup and worker pool

.github/instructions/TODO.md

@@ -2,11 +2,6 @@
 
 > Completed tasks moved to [DONE](./DONE.md). Remaining tasks in [BACKLOG](./BACKLOG.md).
 
-## Cloudflare Workers
-
-- [x] Adjust `frontend/src/main.ts` to use `VITE_PUBLIC_APP_URL` for API requests instead of hardcoded `/api/...` paths.
-- [x] Adjust `frontend/src/main.ts` to use `VITE_PUBLIC_WS_URL` for WebSocket connections instead of hardcoded `wss://...` paths.
-
 ## Frontend Tests
 
 ### User Frontend