fix(style): fix authorize popup button overlap in Firefox

[maruthang]

Description

Add display: flex to .authorize inside .auth-btn-wrapper to override the display: inline from the global .btn.authorize rule in _buttons.scss. Firefox does not automatically blockify inline elements inside flex containers (unlike Chrome), causing the Authorize and Close buttons in the authorization popup to overlap.

Motivation and Context

Fixes #6649

The Authorize popup dialog buttons overlap in Firefox because .btn.authorize sets display: inline, which Firefox doesn't auto-blockify inside the flex container .auth-btn-wrapper.

How Has This Been Tested?

• Added a Cypress E2E regression test (test/e2e-cypress/e2e/bugs/6649.cy.js) that opens the authorize popup and verifies the Authorize and Close buttons do not horizontally overlap
• Verified existing unit tests pass (829 tests, all passing)

Screenshots (if appropriate):

N/A — CSS-only fix, visual overlap issue in Firefox

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.