[FRONTEND] Navbar buttons to gallery, merch pages

[yrska]

🌟 User Story

As a online user,
I want to be able to access each page in one click,
so that I do not have to go through the hamburger menu each time to get to my desired page.

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🎯 Acceptance Criteria

• Places buttons with the correct typography (matching the events, home, etc. buttons on the header).
• Links the buttons to their corresponding pages.
• Tests for responsiveness.

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📊 Definition of Done (DoD)

• Acceptance criteria met
• Agreed tests written
• Agreed documentation in GitHub wiki
• PR reviewed

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🔗 Dependencies

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📚 Additional Context