MHR UI - ToD| Add a Single User Acknowledgment Checkbox For Document Uploads

Staff requested a single acknowledgment checkbox that records the filer’s confirmation that all required documents in the checklist were uploaded. This creates accountability and supports clearer rejection reasoning when items are missing.
### Requirements
- Add one acknowledgment checkbox on the review page. The checkbox records attestation only
- The review page must block submission until the acknowledgment checkbox is selected.
- Store the acknowledgment with the submission record for staff visibility during review and any later audit
- Expose the acknowledgment status and text in the staff queue detail view and in any generated rejection letter context.

Start by locating the review page, submission record, staff queue detail view, and generated rejection letter context. Trace how review submissions are validated and stored, then identify the existing staff and letter displays; done means the required acknowledgment is enforced, persisted, visible to staff, and included in rejection context.

Written by the indexing model from the issue text.