Add optional Hermes Tweet read backend

[kriptoburak]

Summary

• add a read-only Hermes Tweet/Xquik backend for selected Puck read tools
• keep X OAuth as the default when PUCK_CLIENT_ID is present
• keep write, edit, delete, media, mentions, and auth paths on X OAuth
• document PUCK_READ_BACKEND plus Hermes Tweet/Xquik key, base URL, and timeout settings

Validation

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