Bump @angular/compiler from 19.2.13 to 20.3.9 in /frontend

Bumps [@angular/compiler](https://github.com/angular/angular/tree/HEAD/packages/compiler) from 19.2.13 to 20.3.9.
- [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/20.3.9/packages/compiler)

---
updated-dependencies:
- dependency-name: "@angular/compiler"
  dependency-version: 20.3.9
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

frontend/package.json

@@ -74,7 +74,7 @@
         "@angular/animations": "19.2.13",
         "@angular/cdk": "19.2.17",
         "@angular/common": "19.2.13",
-        "@angular/compiler": "19.2.13",
+        "@angular/compiler": "20.3.9",
         "@angular/core": "19.2.13",
         "@angular/forms": "19.2.13",
         "@angular/localize": "19.2.13",