Improve landing page product positioning

[Difficult-Burger]

Summary

This updates the landing page so it better reflects the current Gibwork product: funded crypto bounties, tasks, services, verified submissions, wallet-native payouts, and mobile-friendly contributor workflows.

Changes

• Repositions the hero from a generic talent marketplace message to a clearer funded-work/proof/payout message.
• Adds a new ProductFlow section that explains the creator and contributor workflow:
  • create funded work
  • collect reviewable submissions
  • approve and pay via wallet-native rewards
• Updates the LookingFor section copy and sample work items to match GitHub PR bounties, product walkthroughs, and USDC rewards.
• Updates site metadata to match the new positioning.
• Adds accessible labels for the mobile navigation open/close controls.

Verification

• npx tsc --noEmit
• git diff --check
• Local browser QA at http://localhost:3020
  • desktop hero renders with the updated positioning
  • desktop workflow section renders without overlap
  • mobile hero wraps cleanly at 390px width
  • mobile workflow cards stack cleanly
  • mobile navigation menu opens and shows expected links

Notes

npm run build is currently blocked locally by next/font timing out while fetching Inter from Google Fonts. The app runs in dev after Next falls back to a local font, and the TypeScript check passes. This appears unrelated to this PR because the font import already exists in app/layout.tsx.

[vercel]

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