feat(scheduler): add folder_scan_enabled toggle to SchedulerConfig

- Add folder_scan_enabled boolean field (default false) to SchedulerConfig
- Update data/config.json example with new field
- Add checkbox to setup.html and include in JS payload
- Handle field in auth.py setup endpoint
- Expose field in scheduler API response
- Log and return field in scheduler_service.py
- Update docs/CONFIGURATION.md and docs/ARCHITECTURE.md
- Update index.html UI, app.js and scheduler-config.js handlers
- Verified backward compatibility: old configs load with default False

src/server/api/scheduler.py

@@ -31,6 +31,7 @@ def _build_response(config: SchedulerConfig) -> Dict[str, Any]:
             "schedule_time": config.schedule_time,
             "schedule_days": config.schedule_days,
             "auto_download_after_rescan": config.auto_download_after_rescan,
+            "folder_scan_enabled": config.folder_scan_enabled,
         },
         "status": {
             "is_running": runtime.get("is_running", False),