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/models/auth.py

@@ -73,6 +73,9 @@ class SetupRequest(BaseModel):
     scheduler_auto_download_after_rescan: Optional[bool] = Field(
         default=False, description="Auto-download missing episodes after rescan"
     )
+    scheduler_folder_scan_enabled: Optional[bool] = Field(
+        default=False, description="Run folder maintenance during scheduled run"
+    )
     
     # Logging configuration
     logging_level: Optional[str] = Field(