fix: stabilize maintenance flow run/resume and procedural scrolling

backend/app/api/endpoints/maintenance_schedules.py

@@ -51,7 +51,9 @@ async def create_schedule(
 ):
     """Create a cron schedule for a maintenance flow. One per flow."""
     # Verify user's team owns the tree
-    await _get_tree_or_403(data.tree_id, current_user, db)
+    tree = await _get_tree_or_403(data.tree_id, current_user, db)
+    if tree.tree_type != "maintenance":
+        raise HTTPException(status_code=400, detail="Schedules are only supported for maintenance flows")
 
     # Check no existing schedule for this tree
     existing = await db.execute(