docs: update README for current backend and React frontend (!5) · Merge requests · TC DATA - Data Solutions / Proofs of concept / Data Quality Assessment

## Summary

- Replace the obsolete Streamlit setup instructions - Document the current React/Vite frontend - Add backend installation and execution instructions - Add direct core-library usage examples - Document the API flow, supported dataset formats, and local persistence

## Validation

- Markdown formatting checked - `git diff --check` passed - Only `README.md` is changed

docs: update README for current backend and React frontend

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