Prefill bulk add form from JSON file

**Use case**: I have 57 records to create.

**Idea**: I put them in a JSON file, as a list of records. I go to the `Bulk Add` form, click `Browse`, pick my file and the 57 forms get filled with the provided data.

Some notes:
- It could be `{data: [{record1}, {record2]}` like a JSON dump from the server
- If `id` and `last_modified` are present, they are taken into account

Start by locating the Bulk Add form and its Browse control, then trace how records are represented and added to the form. Support a JSON list or a data-wrapped list, including id and last_modified when present, and verify that the selected file populates all record forms.

Written by the indexing model from the issue text.