Refresh landing page and legacy reference paths

[turin-dev]

Summary

• Replace the placeholder homepage with a product-focused rish-mcp landing page.
• Add responsive layout, device preview, feature/product sections, setup flow, FAQ, and calls to action.
• Refresh page metadata and keep the usage-guide links pointed at the default master branch.
• Correct legacy before/ reference paths for the Docker context, component names, and signing script.

Validation

• cd web && npm run lint ✅
• cd web && npm run build ✅
• docker compose -f before/docker-compose.yml config --quiet ✅ (only unset local environment-variable warnings)
• docker build --progress=plain -f before/server/Dockerfile before/server ✅
• git diff --check ✅

Notes

• The legacy Docker build reports four existing npm audit findings (2 moderate, 2 high); no dependency changes are included in this PR.
• The local legacy Node build could not run without its local node_modules, but the clean Docker build completed successfully.
• This PR does not merge or create a release/tag.