ci(astro): bump checkout + setup-node to v5 (Node 24 runner)

GitHub deprecation: Node 20 actions will be forced to Node 24 by June 2026. actions/checkout@v5 and actions/setup-node@v5 ship with Node 24 internally.

Author: MajorTal

.github/workflows/publish-astro.yml

@@ -63,7 +63,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           # Need history depth for `npm version` to look sane and for the
           # commit-then-push step to operate against the current HEAD.
@@ -74,7 +74,7 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Setup Node
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v5
         with:
           node-version: '22'
           # registry-url tells setup-node to write a project-level .npmrc