chore: add conditional radius and remove min width

[amandaye0h]

Description

Refines button base, addressing:

• BorderRadius
• Conditional Sizing

Related issues

Fixes:

Manual testing steps

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Screenshots/Recordings

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After

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• I've followed MetaMask Contributor Docs
• 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.

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