MNTOR-5282 - Enforce background for breach alert email images

[codemist]

References:

Jira: MNTOR-5282

Description

Unfortunately, the workaround only worked on Gmail iOS, not Gmail Android. I decided to move forward by applying the background colours directly into the images themselves and enforcing light mode where possible. Light mode enforcement still doesn’t fully work in Gmail since the client can continue to dark-mode the image, but embedding the background directly into the asset should at least keep the content accessible and legible. This is the best approach I can implement right now to maintain readability across clients.

As discussed also can’t delete the old images right now, but I’d still like to keep the new ones I introduced for the different email variant experiments. I stored them using a breach-alerts-YYYYMMDD naming format so we can keep track of iterations more easily while we continue testing and refining the templates.

Screenshot (if applicable)

Not applicable.

How to test

Checklist (Definition of Done)

• Localization strings (if needed) have been added.
• Commits in this PR are minimal and have descriptive commit messages.
• I've added or updated the relevant sections in readme and/or code comments
• I've added a unit test to test for potential regressions of this bug.
• If this PR implements a feature flag or experimentation, I've checked that it still works with the flag both on, and with the flag off.
• If this PR implements a feature flag or experimentation, the Ship Behind Feature Flag status in Jira has been set
• Product Owner accepted the User Story (demo of functionality completed) or waived the privilege.
• All acceptance criteria are met.
• Jira ticket has been updated (if needed) to match changes made during the development process.
• Jira ticket has been updated (if needed) with suggestions for QA when this PR is deployed to stage.

[Vinnl]

For some extra polish, you could add some padding to the background colours, and maybe give them rounded corners, to stand out a little less starkly against dark backgrounds.

(But also: screw hacky dark modes :P)