Add button to show and hide access token

[stdevi]

Follow up to #878

Before the change:

After the change:

Motivation and Context

Currently, the access_token.substring(0, 25) is shown. However, when the token is longer, showing only a substring is insufficient, as a user needs to navigate to the token response and copy the access token from there.

Types of changes

• 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 change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally