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/auth.py

@@ -76,6 +76,8 @@ async def setup_auth(req: SetupRequest):
             config.scheduler.schedule_days = req.scheduler_schedule_days
         if req.scheduler_auto_download_after_rescan is not None:
             config.scheduler.auto_download_after_rescan = req.scheduler_auto_download_after_rescan
+        if req.scheduler_folder_scan_enabled is not None:
+            config.scheduler.folder_scan_enabled = req.scheduler_folder_scan_enabled
         
         # Update logging configuration
         if req.logging_level: