Bump @angular/platform-browser from 19.2.14 to 21.0.5 in /frontend

Bumps [@angular/platform-browser](https://github.com/angular/angular/tree/HEAD/packages/platform-browser) from 19.2.14 to 21.0.5.
- [Release notes](https://github.com/angular/angular/releases)
- [Changelog](https://github.com/angular/angular/blob/main/CHANGELOG.md)
- [Commits](https://github.com/angular/angular/commits/v21.0.5/packages/platform-browser)

---
updated-dependencies:
- dependency-name: "@angular/platform-browser"
  dependency-version: 21.0.5
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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