ci: Pin actions in docker-push reusable workflow

(cherry picked from commit fb05f6de0d)

.github/workflows/docker-push.yml

@@ -39,7 +39,7 @@ jobs:
     if: needs.check_secrets.outputs.docker == 'true'
     runs-on: ubuntu-24.04
     steps:
-    - uses: actions/checkout@v6
+    - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
       with:
         fetch-depth: 0
     - uses: ./.github/actions/install-nix-action
@@ -56,7 +56,7 @@ jobs:
     #
     # Push to Docker Hub first
     - name: Login to Docker Hub
-      uses: docker/login-action@v3
+      uses: docker/login-action@5e57cd118135c172c3672efd75eb46360885c0ef # v3.6.0
       with:
         username: ${{ secrets.DOCKERHUB_USERNAME }}
         password: ${{ secrets.DOCKERHUB_TOKEN }}
@@ -64,7 +64,7 @@ jobs:
     - run: docker push ${{ secrets.DOCKERHUB_USERNAME }}/nix:master
     # Push to GitHub Container Registry as well
     - name: Login to GitHub Container Registry
-      uses: docker/login-action@v3
+      uses: docker/login-action@5e57cd118135c172c3672efd75eb46360885c0ef # v3.6.0
       with:
         registry: ghcr.io
         username: ${{ github.actor }}