sync-v2 step 1: worker roles + interactive/bulk queue split

- config: WORKER_ROLE (sync|jobs|all), INTERACTIVE_CONCURRENCY, BULK_CONCURRENCY.
- queue: named queues (interactive/bulk) + enqueue_job() router; sync_bootstrap
  goes to bulk, all other jobs to interactive.
- workers.run: single entrypoint; role=jobs runs both arq consumers (per-queue
  timeout/concurrency), role=sync runs the supervisor, all=both (dev default).
- docker-compose: worker-sync + worker-jobs services (shared image, nofile
  ulimit); backend/Dockerfile; Makefile worker/worker-sync/worker-jobs targets.
- tests repointed to app.queue.get_arq_pool; supervisor behavior unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/sync/actions.py

@@ -273,9 +273,7 @@ async def delete_thread_job(ctx: dict[str, Any], thread_id: str) -> None:
                 .where(Draft.reply_to_message_id.in_(msg_ids))
                 .values(reply_to_message_id=None)
             )
-        await session.execute(
-            update(Draft).where(Draft.thread_id == tid).values(thread_id=None)
-        )
+        await session.execute(update(Draft).where(Draft.thread_id == tid).values(thread_id=None))
         for m in msgs:
             await session.delete(m)
         thread = await session.get(Thread, tid)