fix(ci): add npm fallback for frontend install OOM

.gitea/workflows/cicd-source-checks.yaml

@@ -322,7 +322,11 @@ jobs:
           export NODE_OPTIONS="--max-old-space-size=512"
           export YARN_NETWORK_CONCURRENCY=1
           cd frontend
-          yarn install --immutable --mode=skip-build
+          if ! yarn install --immutable --mode=skip-build; then
+            echo "Yarn install failed; retrying with npm fallback for constrained runner memory"
+            rm -f package-lock.json
+            npm install --ignore-scripts --no-audit --no-fund --prefer-offline
+          fi
 
       - name: Run frontend pre-commit source checks
         env: