Add guard step for skipping Crowdin sync

Add check to skip Crowdin sync if project ID is missing.

Author: cocomarine

.github/workflows/download-translations.yml

@@ -16,6 +16,12 @@ jobs:
   crowdin:
     runs-on: ubuntu-latest
     steps:
+      - name: Skip if Crowdin ID missing
+        run: |
+          if [ -z "${{ secrets.CROWDIN_PROJECT_ID }}" ]; then
+            echo "Skipping Crowdin sync — no project ID set."
+            exit 0
+          fi
       - name: Checkout
         uses: actions/checkout@v4
         with: