workers: don't re-upload handler-returned MinIO keys as local files

handle_process_compliance_service assumed handlers return local temp
paths and re-uploaded each to MinIO. The MCS-150 handler uploads itself
and returns the MinIO key, so the re-upload tried to read a nonexistent
local file and logged a 'File not found' error after the order was
already correctly held at the admin gate. Now we skip files that don't
exist locally and keep the returned key as-is.

scripts/workers/job_server.py

@@ -1265,6 +1265,13 @@ def handle_process_compliance_service(payload: dict) -> dict:
     for fp in file_paths:
         from pathlib import Path
         p = Path(fp)
+        # Some handlers (e.g. MCS-150) upload to MinIO themselves and return the
+        # resulting MinIO key rather than a local temp path. Those keys do not
+        # exist on the local filesystem -- treat them as already-stored and keep
+        # the key as-is instead of trying to re-upload a nonexistent local file.
+        if not p.exists():
+            minio_paths.append(fp)
+            continue
         remote = f"compliance/{effective_order_number}/{p.name}"
         storage.upload(fp, remote)
         minio_paths.append(remote)