CI: Allow Docker Hub login to fail gracefully for fork PRs (#197)

Fork PRs don't have access to repository secrets, causing the login
step to fail and blocking the entire workflow. Adding continue-on-error
lets forks run CI unauthenticated while upstream still benefits from
authenticated pulls.

Co-authored-by: Lukas Kämmerling <lukas.kaemmerling@hetzner-cloud.de>

Author: simPod

.github/workflows/blackbox.yml

@@ -25,6 +25,7 @@ jobs:
           php-version: 8.4
           coverage: none
       - name: Login to Docker Hub
+        continue-on-error: true
         uses: docker/login-action@v3
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}

.github/workflows/checks.yml

@@ -17,6 +17,7 @@ jobs:
           path: ~/.composer/cache/files
           key: dependencies-code-checks
       - name: Login to Docker Hub
+        continue-on-error: true
         uses: docker/login-action@v3
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}

.github/workflows/tests.yml

@@ -49,6 +49,7 @@ jobs:
           path: ~/.composer/cache/files
           key: dependencies-php-${{ matrix.php }}-composer-${{ hashFiles('composer.json') }}
       - name: Login to Docker Hub
+        continue-on-error: true
         uses: docker/login-action@v3
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}