feat: storage management — disk usage, cleanup API, scheduled cleanup task

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/settings.py

@@ -0,0 +1,24 @@
+from fastapi import APIRouter, Depends, HTTPException
+
+from app.api.deps import get_current_user
+from app.models.user import User, UserRole
+from app.services.storage import get_disk_usage
+from app.tasks.cleanup import cleanup_old_data_task
+
+router = APIRouter(prefix="/api/settings", tags=["settings"])
+
+
+@router.get("/storage")
+async def storage_info(user: User = Depends(get_current_user)):
+    return get_disk_usage()
+
+
+@router.post("/cleanup")
+async def trigger_cleanup(
+    retention_days: int | None = None,
+    user: User = Depends(get_current_user),
+):
+    if user.role != UserRole.admin:
+        raise HTTPException(403, "Admin access required")
+    cleanup_old_data_task.delay(retention_days)
+    return {"message": "Cleanup started"}