fix(frontend): clear request timeout on failed requests

[HitanshiThakar]

Description

Moved request timeout cleanup in frontend/src/api.ts into a finally block so timers are cleared for all request paths, including rejected and aborted requests.

Also added focused unit tests covering:

rejected fetch requests
aborted requests

This preserves the existing abort behavior while ensuring timeout cleanup always occurs.

Related Issues

Closes #465

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

npm run test -- api.auth

Result:

15 tests passed

Checklist

• My code follows the code style of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.

[utksh1]

Looks good. The request helper now clears the timeout in a finally block, and the rejection/abort cleanup paths are covered by focused frontend tests. CI is passing.