[Good first issue]: Add “Back to home” link on login page

[FrankezeCode]

Summary

The login page has no way to navigate back to the marketing site. Add a subtle back link consistent with other dark pages like /profile.

What should change?

1. Add a Link to / below the login card (or top of page)
2. Match styling from /profile (“Back to home” or similar)
3. Keep layout mobile-friendly

Acceptance criteria

1. Visible back link on /login
2. Link navigates to home
3. Visual style matches other dark BetterDev pages

Checklist of done conditions:

• Back link added
• Styling uses existing brand classes (text-brand-sky, etc.)
• Works on mobile
• No layout shift or overlap with form

How to test

1. Visit /login
2. Click back link → lands on /
3. Test on narrow viewport

[lucasvass1]

I'm going to work on it.