VOTE-957: Refine registration tool styling

[mlloydbixal]

Jira ticket

VOTE-932
VOTE-957

Description

1. adds styles for:
   a. focus state on state links
   b. masthead styling on mobile
   c. white background on state links list

Deployment and testing

Pre-deploy

1. Insert any required steps to take before merging and running post-deploy.

Post-deploy

1. lando retune
2. npm run build

QA/Test

1. Insert steps to test and confirm the result meets the "definition of done".

Checklist for the Developer

• A link to the JIRA ticket has been included above.
• No merge conflicts exist with the target branch.
• Automated tests have passed on this PR.
• A reviewer has been designated.
• Deployment and testing steps have been documented above, if applicable.

Checklist for the Peer Reviewers

• The file changes are relevant to the task objective.
• Code is readable and includes appropriate commenting.
• Code standards and best practices are followed.
• QA/Test steps were successfully completed, if applicable.
• Applicable logs are free of errors.