fix(worker): don't revive a cancelled job when requeuing a busy asset (C-3.10)

The asset-busy and claim-fail branches wrote status='queued' unconditionally, so a
pause/cancel the route had just written was clobbered back to queued and the job
silently revived. New _requeue_if_running does the requeue as a conditional UPDATE
(...WHERE status='running'), a no-op once the route has moved the job off 'running'.

backend/app/worker.py

@@ -66,6 +66,22 @@ def _job_status(job_id: int) -> str | None:
         ).scalar()
 
 
+def _requeue_if_running(job_id: int, phase: str) -> None:
+    """Put the job back to 'queued' for a later retry, but ONLY while it is still 'running'. The
+    route flips status to paused/cancelled to stop a job; a blind `status='queued'` here would
+    clobber that and silently revive a job the user just cancelled. The conditional WHERE makes the
+    requeue a no-op unless we still own a running job."""
+    with SessionLocal() as db:
+        db.execute(
+            text(
+                "UPDATE download_jobs SET status='queued', phase=:phase, updated_at=now() "
+                "WHERE id=:id AND status='running'"
+            ),
+            {"id": job_id, "phase": phase},
+        )
+        db.commit()
+
+
 def _parse_upload_date(raw) -> date | None:
     if not raw:
         return None
@@ -179,13 +195,13 @@ def _process_job(job_id: int) -> None:
         return
     if asset_status == "downloading":
         # Another worker owns this asset; wait and let the job be reclaimed later.
-        _set_job(job_id, status="queued", phase="waiting")
+        _requeue_if_running(job_id, "waiting")
         time.sleep(2)
         return
 
     # asset_status == "pending": try to win the download / edit.
     if not _claim_asset(asset_id):
-        _set_job(job_id, status="queued", phase="waiting")
+        _requeue_if_running(job_id, "waiting")
         time.sleep(2)
         return
 
@@ -414,7 +430,7 @@ def _download(job_id: int, asset_id: int, source_kind: str, source_ref: str, spe
         )
 
         layout, retention_days = _download_settings()
-        rel = storage.rel_path(meta, ext, layout)
+        rel = storage.rel_path(meta, ext, layout, asset_id=asset_id)
         thumb = _find_thumbnail(staging, produced)
         storage.place_file(produced, settings.download_root, rel)
         nfo_ok = storage.write_sidecars(settings.download_root, rel, meta, thumb)