feat: add drag-and-drop reorder to list detail page items

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

routers/lists.py

@@ -406,3 +406,17 @@ async def reorder_list_item(
         filters["parent_item_id"] = None
     await repo.move_in_order(item_id, direction, filters=filters)
     return RedirectResponse(url=f"/lists/{list_id}", status_code=303)
+
+
+@router.post("/{list_id}/items/reorder-all")
+async def reorder_all_list_items(
+    list_id: str,
+    request: Request,
+    item_ids: str = Form(...),
+    db: AsyncSession = Depends(get_db),
+):
+    repo = BaseRepository("list_items", db)
+    ids = [i.strip() for i in item_ids.split(",") if i.strip()]
+    if ids:
+        await repo.reorder(ids)
+    return RedirectResponse(url=f"/lists/{list_id}", status_code=303)