Issue: #3008

# Description
Migrate navigation menu styles to Tailwind.

# Demo 
|Before| After|
|-|-|
| <img width="450" height="642" alt="image"
src="https://github.com/user-attachments/assets/b08f976c-496e-4ce7-b4c7-2b721ac5b738"
/>| <img width="406" height="699" alt="image"
src="https://github.com/user-attachments/assets/46a14373-bf93-42cc-af5f-002f7f6691e7"
/>
|<img width="445" height="646" alt="image"
src="https://github.com/user-attachments/assets/adc79dce-197f-436b-8c6a-e8c79488c6a1"
/> | <img width="428" height="556" alt="image"
src="https://github.com/user-attachments/assets/5b9c30d2-e220-4a00-83f5-4f017d898840"
/>


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# AI Disclosure
Implemented using claude-opus-4.6 via Antigravity, self-reviewed by me.

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*Cherry-picked from https://github.com/SalmanNajah/gumroad/pull/3 by
@SalmanNajah*

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Co-authored-by: Salman Najah <salmannajah123@gmail.com>