Explain better how the verification works
_Originally created by @sajolida on [#14997 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/14997)_
https://gitlab.tails.boum.org/tails/tails/-/issues/14945#note_34484:
« When I see “Verification failed” I immediately had the feeling that I
want to know why. Could we add something like “Checksums did not match”?
Or something similar? »
Feature Branch: web/14997-explain-better-verification-and-failure
Parent Task: tails/tails#12328
### Related issues
- **Related to** tails/tails#14998
issue