Keep master_core off Qt so the web image starts

master_core imported safe_title from font_manager, which imports PyQt5 at
module load. The web extra installs no Qt, so `ujm-web` crashed on startup
with "No module named 'PyQt5'" inside the container. safe_title is only a
UTF-8 round-trip, so master_core now carries its own Qt-free copy; the
desktop path keeps using font_manager's.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015UXA39Sh9coAx4FhRkd8R2

master_core.py

@@ -7,7 +7,13 @@ import numpy as np
 from mutagen.mp3 import MP3
 from mutagen.easyid3 import EasyID3
 
-from font_manager import safe_title
+
+def safe_title(title):
+  # Deliberately not font_manager.safe_title: that module imports PyQt5 at load
+  # time, and master_core is on the Qt-free web path (the `web` extra has no Qt).
+  if not title:
+    return title
+  return title.encode('utf-8', errors='replace').decode('utf-8')
 
 
 def _try_mp3_tags(file_path):