Add optional Hermes Tweet read backend

[kriptoburak]

Summary

• add an optional Hermes Tweet-compatible Xquik read backend for tweet search and user timeline tools
• prefer HERMES_TWEET_API_KEY, while keeping XQUIK_API_KEY and XQUIK_BASE_URL as compatibility aliases
• keep existing Twitter credential/API modes as fallback and leave write tools on the existing paths
• add get_hermes_tweet_backend_status so clients can verify configuration without exposing secrets
• document the optional backend in README and add a lightweight test script for backend URL/key/normalization behavior

Validation

• pnpm install --frozen-lockfile
• pnpm build
• pnpm test
• changed-file external public-link check: checked=2 failures=0
• git diff --check