fix: skip optional deps in backend CI to resolve missing bare-url lock file error

Author: mftee

.github/workflows/ci.yml

@@ -30,7 +30,7 @@ jobs:
           cache-dependency-path: backend/package-lock.json
 
       - name: Install dependencies
-        run: npm ci --legacy-peer-deps
+        run: npm ci --omit=optional
 
       - name: Lint
         run: npm run lint