File attachment: Investigate more specific error messaging for client side

[Abi-Nada]

Description:

From incident: #incident-2024-10-03-file-extension-error

For the Copyright Board of Canada form, we currently do not throw an error message on the client side when an end-user uploads a ".cfb" attachment. This means that they go through the process of filling out the entire form, and only when they hit "Submit" is when they get a generic error message:

Acceptance Criteria:

• Investigate more specific error messaging for the client side, so when the client uploads an attachment that contains ".cfb", it is rejected then (vs later when they hit Submit)