Improve link accessibility and styling in DataFormBranding

[imran-s-creator]

This PR improves the link styling and accessibility of the Mathesar branding link in forms.

Changes include:

• Added smooth transitions for color and text-decoration
• Enhanced hover state with proper underline styling (thickness and offset)
• Added focus state for keyboard navigation
• Added focus-visible state for better keyboard user experience
• Added visited link styling to maintain theme consistency
• Added active state with opacity feedback

These improvements ensure better accessibility across all interaction states while maintaining theme compatibility.

Fixes #4769
This PR updates the Mathesar link on the form fillout page to use the theme’s base text color and adds an underline on hover and focus. It ensures the link looks visually aligned and accessible in both light and dark themes.

##Technical details

Updated link color to use the theme’s base text color (--color-fg-base) instead of muted text
Added underline on hover and focus states for accessibility
Scoped styles within .form-branding a to avoid global overrides
Verified appearance in both light and dark themes

Updated link color to use the theme’s base text color (--color-fg-base) instead of muted text
Added underline on hover and focus states for accessibility
Scoped styles within .form-branding a to avoid global overrides
Verified appearance in both light and dark themes

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the develop branch of the repository
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

Developer Certificate of Origin

Developer Certificate of Origin

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

[Anish9901]

Hey @imran-s-creator, There are 37 file changes, in your PR and these seem to be unrelated changes. Before we can review this can you please revert all unnecessary changes and make minimal changes for fixing the issue your are trying to solve.

[Anish9901]

@imran-s-creator Can you post a screenshot of the logo with your changes?