Fix error handling in embedding worker: capture actual exception message

The except clause wasn't binding the exception to a variable, so
str(Exception) stored the class name "<class 'Exception'>" instead of
the actual error message. Now properly captures `as e` and stores str(e).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/haunt_fm/services/embedding_worker.py

@@ -119,14 +119,14 @@ async def run_worker():
                         try:
                             await _process_track(session, track)
                             logger.info("Embedded: %s - %s", track.artist, track.title)
-                        except Exception:
+                        except Exception as e:
                             logger.exception("Failed to embed %s - %s", track.artist, track.title)
                             await session.execute(
                                 update(Track)
                                 .where(Track.id == track.id)
                                 .values(
                                     embedding_status="failed",
-                                    embedding_error=str(Exception),
+                                    embedding_error=str(e),
                                 )
                             )
                             await session.commit()