[codex] Update bistro requirements docs

[satvik007]

Summary

• Replace the old docs/requirements.md source with the new canonical docs/REQUIREMENTS.md requirements spec.
• Add the linked docs/CONTEXT.md, docs/MANUAL.md, and docs/AUTOMATED.md files so docs-folder markdown references resolve.
• Remove the legacy nested docs/manual-testing/requirements.md and docs/automated-testing/requirements.md files.
• Update copied repository links from Hypersequent/food-delivery-demo to Hypersequent/bistro-e2e.

Validation

• npm run lint
• Custom docs link audit: checked 4 markdown files and verified local docs links plus requirement anchors resolve.