refactor(ramp): persist and format amount in build quote view

[wachunei]

Description

This PR makes the following changes:

• It formats the amount input in the Buy flow during editing. Previously, the amount was formatted only after editing was completed.
• It persists the amount input when the payment method is updated. Previously, the amount was cleared and reset to 0.

Related issues

Fixes: https://consensyssoftware.atlassian.net/browse/RAMPS-1465

Manual testing steps

1. Go to Buy/Sell flow
2. Enter an amount: It must be formatted as it is being entered (only Buy flow)
3. Finish the amount editing
4. Switch payment method: The amount must not reset to 0

Screenshots/Recordings

Before

amount_before.mp4

After

amount_after.mp4

Pre-merge author checklist

• I’ve followed MetaMask 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.

[NicolasMassart]

Looks good to me.

[github-actions]

Bitrise

✅✅✅ pr_smoke_e2e_pipeline passed on Bitrise! ✅✅✅

Commit hash: 89fec7f
Build link: https://app.bitrise.io/app/be69d4368ee7e86d/pipelines/46d437ab-b934-4562-8c72-4d07921cd521

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

[bkirb]

@wachunei LGTM I verified the buy and sell flows ✅

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.53%. Comparing base (18e2f11) to head (d48b8a0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9039      +/-   ##
==========================================
- Coverage   45.54%   45.53%   -0.01%     
==========================================
  Files        1272     1272              
  Lines       31236    31232       -4     
  Branches     3188     3187       -1     
==========================================
- Hits        14225    14221       -4     
  Misses      16171    16171              
  Partials      840      840              

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud