Add NVIDIA env config and CI quality gates

[puppe1990]

Summary

• add NVIDIA provider support with keys sourced from .env
• add automated tests, ESLint, Prettier, Husky pre-commit, and GitHub Actions CI
• format the codebase and resolve all current lint/prettier issues

Validation

• npm test
• npm run lint
• npm run format:check
• npm run ci

[chatgpt-codex-connector]

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