build(deps): bump withastro/action from 4 to 6

Bumps [withastro/action](https://github.com/withastro/action) from 4 to 6.
- [Release notes](https://github.com/withastro/action/releases)
- [Commits](withastro/action@v4...v6)

---
updated-dependencies:
- dependency-name: withastro/action
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/build-and-deploy.yml

@@ -23,7 +23,7 @@ jobs:
         run: echo 0 | sudo tee /proc/sys/kernel/apparmor_restrict_unprivileged_userns
 
       - name: 🚀 Install, build, and upload artifact
-        uses: withastro/action@v4
+        uses: withastro/action@v6
         with:
           node-version: 24
   deploy: