Add bounty issue discovery homepage

[Zhenvip]

Closes #43

Summary

• replace the root page with a cross-repository bounty issue discovery list
• move the existing deployment guide to /deploy
• persist GitHub issue metadata on bounty records so the list can show titles, status, links, dates, and excerpts
• add filtering/sorting helpers with tests
• sync package-lock.json with the existing package.json @pvium/sdk dependency so npm installs work cleanly

Verification

• npm test
• npm run typecheck
• npm run build
• git diff --check

[vercel]

@CharlieLZ is attempting to deploy a commit to the Bytegum Team on Vercel.

A member of the Team first needs to authorize it.

[Zhenvip]

The Vercel check is failing on fork deployment authorization for the Bytegum team. I verified the app locally with:

• npm test
• npm run typecheck
• npm run build
• git diff --check