feat: deliver complete FoodGraph competition workbench

[teopaleface]

What changed

• delivers the complete FoodGraph competition workbench and local API
• adds grounded search, safe Query Lab, Graph Explorer, audit, conversations, recipes, voice and persistent workspace history
• adds the reproducible notebook, validated fixtures, evaluation artifacts, contributor documentation and deployment configuration
• adds the interactive presentation, committed fallbacks, screenshots and validation tooling

Why

This consolidates the complete competition reference implementation into one reproducible branch that can be reviewed and merged as a coherent project.

Validation

• conda run -n environment python -m pytest -q — 171 passed, 57 subtests
• conda run -n environment python scripts/validate_artifacts.py
• frontend: npm run typecheck && npm run build && npm run check:react
• presentation: npm run check && npm run build

Notes

• .env and local credentials remain ignored.
• transient Playwright runtime caches are excluded; reviewed screenshots and presentation fallbacks are included.
• React Doctor reports advisory recommendations only; builds and tests pass.