chore(deps): bump astro from 5.13.5 to 5.15.3

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.13.5 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
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -16,7 +16,7 @@
     "@astrojs/cloudflare": "^12.6.6",
     "@astrojs/mdx": "^4.3.4",
     "@tailwindcss/vite": "^4.1.11",
-    "astro": "^5.13.4",
+    "astro": "^5.15.3",
     "astro-icon": "^1.1.5",
     "katex": "^0.16.22",
     "lucide-astro": "^0.536.0",