fix(navbar): unify login/register navbar into shared PublicNavBar component

[Hunter69240]

Description

The Login and Register pages each hardcoded their own copy of the navbar using
premium-nav-links / premium-btn classes, which are not defined anywhere in
App.css. This caused the nav links ("Home", "Login", "Register") to render
with no spacing at all, running together edge-to-edge (e.g. "HomeLoginRegister")
on both desktop and mobile, with no hamburger menu on small screens.

This PR removes the duplicated, unstyled navbar markup from both pages and
replaces it with a new shared PublicNavBar component, styled using the site's
existing .landing-nav / .nav-text-link classes (the same ones already used
correctly on the Home page). This keeps the visual design consistent across
Home, Login, and Register, and restores proper mobile behavior via react-bootstrap's
Navbar.Toggle/Navbar.Collapse (hamburger menu).

Closes #14

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)

Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings or console errors.
• I have tested my changes locally and verified they work as expected.
• Any dependent changes have been merged and published in downstream modules.

Screenshots / Screen Recordings

Before: Login/Register navbar links rendered edge-to-edge with no spacing.

After: Navbar links properly spaced, consistent with Home page styling,
includes working hamburger menu on mobile.

[Hunter69240]

@udaycodespace could you add the ECSoC26 label to this PR so Sentinel picks it up? Thanks!

[udaycodespace]

@udaycodespace could you add the ECSoC26 label to this PR so Sentinel picks it up? Thanks!

LGTM. Thanks for the clean refactor and for resolving the reported navbar issue.

1. One minor suggestion for future improvements would be to use React Router navigation (as={NavLink} / to) for Navbar.Brand instead of href to avoid a full page reload.
2. This isn't blocking, so approving.

[Hunter69240]

@udaycodespace could you add the ECSoC26 label to this PR so Sentinel picks it up? Thanks!

LGTM. Thanks for the clean refactor and for resolving the reported navbar issue.

1. One minor suggestion for future improvements would be to use React Router navigation (as={NavLink} / to) for Navbar.Brand instead of href to avoid a full page reload.
2. This isn't blocking, so approving.

Gotcha , Thank you for info , will look into it in future