Persist biometrics when manually locking app

[Cal-L]

What is this about?

At the time of writing, there are some cases where we persist biometric credentials (Killing and reopening the app while unlocked) and other times where we clear them. (Ex. We clear them when a user manually locks the app). To keep the behavior consistent and to provide a better user experience, this task will update the app's behavior to persist biometric credentials when a user manually locks the app. As a result, a user with biometric credentials previously enabled will be able to use biometrics to unlock once they've manually locked it. Here is the thread with involvement from individuals from wallet UX, security, and mobile platform team - https://consensys.slack.com/archives/C06FXU326RL/p1743541401398509

Scenario

• Create a new wallet with biometrics enabled

• Go into settings and manually lock the app

• User should see the biometrics button when landing on the login screen

• Pressing the biometrics button should prompt biometrics, which upon success, will unlock the wallet

• Create a new wallet with biometrics enabled

• Go into settings and manually lock the app

• Kill the app and re-open the app

• User should see the biometrics button when landing on the login screen

• Pressing the biometrics button should prompt biometrics, which upon success, will unlock the wallet

Design

No response

Technical Details

• Do not clear biometrics when manually locking the app

Threat Modeling Framework

No response

Acceptance Criteria

No response

Stakeholder review needed before the work gets merged

• [ ] Engineering (needed in most cases)
• [ ] Design
• [ ] Product
• [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
• [ ] Security
• [ ] Legal
• [ ] Marketing
• [ ] Management (please specify)
• [ ] Other (please specify)

References

This is a follow up from this PR - https://github.com/MetaMask/metamask-mobile/pull/14396