Bump astro from 5.12.9 to 5.15.3

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.12.9 to 5.15.3.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/astro@5.15.3/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.15.3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]