fix: polish mobile responsive layout

[ScryUser]

Description

Fixes the mobile responsive polish bounty for #824 by tightening the 375px and 768px layouts across the bounty cards, navigation, hero terminal, activity feed, and footer.

Changes include:

• bounty cards now wrap repo/title/skill/reward/meta content safely on narrow screens
• mobile card status badges are placed in normal flow to avoid overlapping the reward/meta row
• bounty page action controls stack full-width at 375px and return inline at larger breakpoints
• mobile hamburger has accessible expanded/collapsed state and closes on route changes
• hero terminal uses a compact mobile command, smaller mobile type, full-width CTA behavior, and wrapped stats
• activity feed detail text wraps instead of clipping or pushing outside the viewport
• footer columns and token address are constrained to avoid overflow
• global overflow guards prevent accidental horizontal scrolling
• restores the shared src/lib modules required by existing frontend imports and narrows the root .gitignore lib/ rule so frontend source libs can be tracked

Closes #824

Solana Wallet for Payout

Wallet: C2z3FWAacvSYVrrkfpk6nQyNhF4t3z7t9iXRW1xfZPy1

Type of Change

• Bug fix
• Responsive/mobile polish
• Test addition/update

Checklist

• One PR per bounty
• Bounty cards stack and wrap properly on mobile
• Navigation hamburger opens, closes, and exposes accessible state
• Hero terminal is readable on small screens
• Footer does not overflow
• No horizontal scroll at 375px or 768px in viewport QA
• No hardcoded secrets or private keys

Testing

• npm test -- mobile-responsive-polish.test.tsx
• npm run build
• git diff --check
• Local Chrome viewport QA at 375x812 and 768x1024 for / and /bounties with mocked bounty API data
  • documentElement.scrollWidth === innerWidth
  • body.scrollWidth === innerWidth
  • no measured elements outside the viewport bounds
  • mocked mobile bounty card rendered at 343px width with status below reward/meta content