Improve landing app handoff metadata

[chedger]

Summary

• Updates the landing-page metadata from generic talent-marketplace language to the current onchain work flow: fund tasks, submit proof, and claim USDC/Solana rewards.
• Adds canonical/OpenGraph/Twitter metadata, iOS Smart App Banner metadata, and SoftwareApplication JSON-LD for clearer search/social/app handoff signals.
• Splits the hero action into two measurable intents: Find paid tasks and Post a task, with lightweight proof chips for escrow-backed tasks, GitHub bounties, and wallet payouts.

Why

The current homepage still leads with broad "Find Talent, Find Work" positioning. This keeps the update focused: it improves first-viewport intent clarity and app handoff signals without duplicating the larger visual redesign PRs already open.

Validation

• git diff --check

Build/lint were not run because this local environment has no npm, yarn, pnpm, or node_modules available.

Notes

Submitted for the funded Gibwork landing-page/GitHub enhancement task: https://app.gib.work/tasks/b7c2a3c9-c412-4613-9cfb-d8a5f54d14b7

Payout is contingent on Gibwork review and approval; this PR does not assume guaranteed acceptance.

[vercel]

@chedger is attempting to deploy a commit to the gibwork Team on Vercel.

A member of the Team first needs to authorize it.