Changelog:
- Added ProxyFix middleware to support reverse proxy headers (X‑Forwarded)
- Improved redirect URI handling with per-request calculation and environment fallback
- Enabled persistent sync settings via settings.json and new PLEXYTRACK_DATA_DIR variable
- Updated Docker Compose to persist data across container restarts
- Added load_settings and save_settings helpers for persistent state management
- Updated .env.example, .gitignore, and README with new configuration and setup instructions