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/config.py

@@ -39,6 +39,11 @@ class SchedulerConfig(BaseModel):
         description="Automatically queue and start downloads for all missing "
                     "episodes after a scheduled rescan completes.",
     )
+    folder_scan_enabled: bool = Field(
+        default=False,
+        description="Run folder maintenance (NFO repair, folder renaming, "
+                    "poster checks) during the scheduled run.",
+    )
 
     @field_validator("schedule_time")
     @classmethod