Store remote review rounds as manifests

[NarwhalChen]

Summary

• Store remote round manifests in Worker KV as the source of truth and render review boards from manifest data
• Resolve review UI theme from manifest tokens with brand → repo → default fallback, per token
• Keep legacy self-contained HTML share support while moving manifest-backed boards to r:<id> keys
• Update remote review template/docs and add Worker tests for manifest publish, render, verdict, and theme fallback flows

Verification

• npm test in share-server
• uv run pytest
• uv run ruff check .
• git diff --check

Notes

• Live smoke-tested 4 manifest-backed rounds on a temporary Workers deployment; production deploy still requires Cloudflare auth for the official share server.