fix working directory for node_modules caching

.github/workflows/lint.backend.yml

@@ -4,11 +4,13 @@ on: [push]
 
 jobs:
     lint:
-        working-directory: backend
         runs-on: ubuntu-latest
         strategy:
             matrix:
                 node-version: [lts/*]
+        defaults:
+            run:
+                working-directory: ./backend
         steps:
             - uses: actions/checkout@v4
 
@@ -18,6 +20,7 @@ jobs:
               env:
                   cache-name: cache-node-modules
               with:
+                  working-directory: ./backend
                   # npm cache files are stored in `~/.npm` on Linux/macOS
                   path: ~/.npm
                   key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('**/package-lock.json') }}