fix: update input handling in useInputHandler to support BACK key functionality

[amitabh94]

Description

This PR updates the handleKeypadChange function in useInputHandler to allow for better input management. The function now also checks for the 'BACK' key press and allows input only if the total number of digits is within the defined limit. This change improves user experience by enabling backspace functionality while maintaining input constraints.

Related issues

Fixes: STAKE-886

Manual testing steps

1. Start the app
2. Go to Earn and input high ETH input such that fiat value is more than 12 digits
3. Click on currency switch button
4. Press back button on keypad and it should edit the fiat amount even though the digits are more than 12

Screenshots/Recordings

Before

fiat.conversion.digits.mp4

After

Fix.unresponsive.keypad.mp4

Pre-merge author checklist

• I’ve followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[github-actions]

Bitrise

✅✅✅ pr_smoke_e2e_pipeline passed on Bitrise! ✅✅✅

Commit hash: ce23c57
Build link: https://app.bitrise.io/app/be69d4368ee7e86d/pipelines/e970c211-cdf2-4904-a545-fe5f6943a9f3

Note

• You can kick off another pr_smoke_e2e_pipeline on Bitrise by removing and re-applying the Run Smoke E2E label on the pull request

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
80.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud