Audiobook player with user accounts and synced progress

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,8 @@
+# secrets and per-user data: never commit
+config.json
+users.json
+sessions.json
+progress.json
+progress_users.json
+*.tmp
+__pycache__/