PR4h fixup: restore strict 1:1 in master.py

Three drifts caught in line-by-line review against original — all reverted
so the lifted body is now byte-identical to the web_server.py original
(after deps.X → global X normalization):

1. `import traceback` was hoisted to module-level imports. Original imports
   it inline inside the except block. Moved back to inline (same behavior,
   but strict location parity).
2. Trailing whitespace on the blank line after analysis_results.append.
3. Trailing whitespace on the blank line inside the wishlist except handler.

Diff against original now produces ZERO differences. Tests still 21/21
passing, ruff clean.

core/downloads/master.py

@@ -29,7 +29,6 @@ import json
 import logging
 import re
 import time
-import traceback
 import uuid
 from dataclasses import dataclass
 from typing import Any, Callable
@@ -626,6 +625,7 @@ def run_full_missing_tracks_process(batch_id, playlist_id, tracks_json, deps: Ma
 
     except Exception as e:
         logger.error(f"Master worker for batch {batch_id} failed: {e}")
+        import traceback
         traceback.print_exc()
 
         is_auto_batch = False