# Design: Persistent ordering + touch-friendly DnD

## Database
- Add `sort_order integer not null default 0` to `bookmarks`.
- Add indexes to support ordered listing:
  - `(user_id, folder_id, sort_order)`

## API
- Extend `Bookmark` DTO/schema with `sortOrder`.
- Add `POST /bookmarks/reorder` similar to existing `/folders/reorder`:
  - Input: `{ folderId: uuid|null, orderedIds: uuid[] }`
  - Validates `orderedIds` is a permutation of all bookmarks for that user+folder (excluding deleted).
  - Transactionally updates `sort_order` for each id.

## Web UI
- Replace native HTML5 drag/drop with a touch-capable approach.
  - Implementation choice: `sortablejs` (small, proven, touch-friendly).
  - Bind Sortable to:
    - Folder header list (per parent group) for folder ordering.
    - Each open folder’s bookmark list for bookmark ordering.
- Root group is rendered as a first-class group and can also be reordered.

## Compatibility
- If the DB schema lacks ordering columns (fresh/old DB), endpoints should return a clear 409 prompting `db:migrate`.