feat(ui): improve responsive navigation (Part of #68)

[jonathanprogram2]

Summary

Improves responsive navigation behavior across the landing page and dashboard.

Changes

• Improved dashboard navbar responsiveness at 360px, 390px, and 768px
• Reduced mobile spacing and sizing for credits/recharge controls
• Hid the profile name on smaller screens to prevent crowding
• Improved landing page navbar spacing at tablet widths
• Reduced navigation text size at 768px
• Reduced Dashboard button size on smaller screens
• Adjusted landing header padding for better tablet alignment

Testing

Tested manually in Chrome DevTools at:

• 360px
• 390px
• 768px

Also verified:

• npm run build passes successfully
• Desktop navbar layout remains unchanged

Part of #68

[vercel]

@jonathanprogram2 is attempting to deploy a commit to the Karan's projects Team on Vercel.

A member of the Team first needs to authorize it.

[Edge-Explorer]

Thanks @jonathanprogram2! Tested locally and the mobile navigation looks much cleaner at 360px–768px viewports with zero build issues. Merging this PR now! 🚀

Looking forward to the next PR for the remaining areas (Stock Chart toolbars and AI Analyst inputs) from #68!