Bump @mui/material from 5.16.7 to 6.4.1 in /frontend

Bumps [@mui/material](https://github.com/mui/material-ui/tree/HEAD/packages/mui-material) from 5.16.7 to 6.4.1.
- [Release notes](https://github.com/mui/material-ui/releases)
- [Changelog](https://github.com/mui/material-ui/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mui/material-ui/commits/v6.4.1/packages/mui-material)

---
updated-dependencies:
- dependency-name: "@mui/material"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Author: dependabot[bot]