fix: Polish mobile bounty card layouts

[NUGMUNCHERS]

Description

Implements mobile responsive polish for bounty cards, navigation, hero terminal, and footer.

Closes #824

Solana Wallet for Payout

Wallet: 5VsD1ZGdTmaXQAbCvS5GMGB4FymyfGZxhbeiTunY6CdD

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• 🎨 Style/UI update
• ♻️ Code refactoring
• ⚡ Performance improvement
• ✅ Test addition/update

Checklist

• Code is clean and follows the issue spec exactly
• One PR per bounty (no multiple bounties in one PR)
• Tests included for new functionality
• All existing tests pass
• No console.log or debugging code left behind
• No hardcoded secrets or API keys

Testing

• Manual testing performed
• Unit tests added/updated
• Integration tests added/updated

Validation performed:

• npm run build
• git diff --check
• Playwright/Edge smoke at 375px and 768px for / and /bounties with mocked bounty data: no horizontal document overflow; hamburger menu opens at both widths.

Note: npm test currently fails on unrelated pre-existing missing legacy test targets and missing @playwright/test dependency.

Screenshots (if applicable)

N/A

Additional Notes

• Restores shared frontend lib utilities/animation variants that current components import, and unignores frontend/src/lib.
• Keeps the main nav in hamburger mode through tablet widths so 768px layouts do not crowd/truncate.
• Improves small-screen wrapping/stacking for hero terminal text, CTA buttons, bounty cards, grid controls, activity feed rows, featured bounties, and footer token copy.