feat(authz): refine audit user page layout and spacing

[jacobo-dominguez-wgu]

Description

Polishing the audit user page. Added an optional borderBottom prop to AuthZTitle that renders a bottom border under the title band, enabled it on the audit user page, and tightened the page spacing (py-5 → py-3). The border is defined with Paragon tokens so it stays theme-aware. The table filter components are smaller but not by a direct modification of this pr but inherited from #251

Closes #242
Figma design

Testing

• Added unit tests for the AuthZTitle borderBottom prop, asserting the title-border-bottom class is present only when the prop is passed.
• Existing AuthZTitle suite still passes (10 tests).
• Go to the specific user (audit user) page and verify the title has a bottom border and the spacing matches the figma design.

Screenshots

Before	After

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.71%. Comparing base (8c8829a) to head (5634c04).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #252   +/-   ##
=======================================
  Coverage   98.71%   98.71%           
=======================================
  Files          80       80           
  Lines        1400     1401    +1     
  Branches      470      472    +2     
=======================================
+ Hits         1382     1383    +1     
  Misses         18       18           

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[dcoa]

I have some nits

[jesusbalderramawgu]

pulled the code locally, looks good. Thank you