UX: File scanning messages - Reporting

Some of this work was done in registration [#3172](https://github.com/orgs/bcgov/projects/123/views/1?filterQuery=3172&pane=issue&itemId=105565307&issue=bcgov%7Ccas-registration%7C3172)

### Describe the problem
Given that the user clicked submit but the files have not finished scanning yet, they keep trying to click submit but they have to wait first.

### **Registration**
If there is an issue found in the file after scanning, show this message on the submission page:
- [ ] `Security issues found in attachments. Please replace [file name], [file name].`

### **Reporting**
Users click "submit" to validate the attachments in reporting [#715](https://github.com/orgs/bcgov/projects/123/views/1?filterQuery=repo%3Abcgov%2Fcas-reporting++-status%3Adone+715&pane=issue&itemId=106976847&issue=bcgov%7Ccas-reporting%7C715). A better user experience would be to have a Validate button.

Given the user is on the sign-off page
- [ ] The "save" button is replaced with "Validate report" [Wireframe](https://www.figma.com/design/LsDmLDCdnJqI8UahyqvOD8/BCIERS-Designs?node-id=37305-8792&t=Cg0OH69ZAG57n8O2-4)

When the user clicks Validate Report
If the file has not finished scanning yet
- [ ] The error alert appears "Scanning in progress for Attachment [field name]: [file name], [field name]: [file name].
Please wait a few minutes, then validate the report again." [Wireframe](https://www.figma.com/design/LsDmLDCdnJqI8UahyqvOD8/BCIERS-Designs?node-id=37310-9630&t=Cg0OH69ZAG57n8O2-4)
- [ ] submit button is disabled

When the user clicks Validate Report
If the scan is completed, and the validation is successful
- [ ] replace the error with success "Report validated. You may now submit." [Wireframe](https://www.figma.com/design/LsDmLDCdnJqI8UahyqvOD8/BCIERS-Designs?node-id=37311-9829&t=Cg0OH69ZAG57n8O2-4)
- [ ] enable the submit button

#### Definition of Done

- [ ] first
- [ ] second
- [ ] third

#### Additional context

- Add any other context about the task here.
- Or here

Start at the reporting sign-off page and review issue #715 alongside the registration work linked as #3172. Trace the attachment validation flow and compare it with the wireframes; the work is done when validation reports scanning or success correctly, and the submit button is disabled or enabled accordingly.

Written by the indexing model from the issue text.