Profile README and CONTRIBUTING have broken and misleading repo links

[kirilly]

The org profile has a few links that 404 or say the wrong thing. Found while clicking through from the org page.

• The CONTRIBUTING link in profile/README.md points to profile/CONTRIBUTING.md. Since the README already lives in profile/, GitHub resolves that to profile/profile/CONTRIBUTING.md, which 404s. It should be CONTRIBUTING.md.
• "API Repository" links to github.com/peanutprotocol/peanut-api, which 404s. CI in peanut-ui references peanut-api-ts everywhere. Either point at the right repo or drop the link and say it's private.
• The README says contracts, sdk, and api are "only accessible through request", but peanut-contracts and peanut-sdk are public (both return 200). Only the API is actually private, so the line is misleading.
• The Discord link in profile/CONTRIBUTING.md is malformed: [Discord]([link-to-discord(https://discord.gg/kVZqXDkrq7)). The invite still works but the markdown renders broken. Should be [Discord](https://discord.gg/kVZqXDkrq7).
• Minor: "Now Hiring!" appears twice in README.md, once above the H1 and once under the logo.

Fix

Correct the four links above and drop the duplicate hiring line.