MPDX-9211 - Add CancelButton component and delete salary calculation mutation for cancellation

[zweatshirt]

Description

• Adds a cancel button on all steps except the Receipt.
• Cancellation deletes the mutation, since the intended result is to completely cancel the request altogether.

Jira ticket

Testing

• Go to reports/salaryRequest > Create new calculation or continue calculation
• Ensure that the Cancel button appears on all form steps except the receipt step.
• Check that the cancellation button successfully deletes the request.

Checklist:

• I have given my PR a title with the format "MPDX-(JIRA#) (summary sentence max 80 chars)"
• I have applied the appropriate labels (Add the label "Preview" to automatically create a preview environment)
• I have run the Claude Code /pr-review command locally and fixed any relevant suggestions
• I have requested a review from another person on the project
• I have tested my changes in preview or in staging
• I have cleaned up my commit history

[github-actions]

Preview branch generated at https://MPDX-9211.d3dytjb8adxkk5.amplifyapp.com

[github-actions]

Bundle sizes [mpdx-react]

Compared against 3e01774

No significant changes found

[canac]

The code works and looks great! I reached out to Joanna in Figma for clarity on whether cancel should delete the request. Can you wait to merge until we hear back?

[canac]

Because of the early return, I don't think calculation?.id can ever be falsy.

Suggested change

disabled={!calculation?.id}