ci: run backend ruff

Author: pablogsal

.github/workflows/ci.yml

@@ -56,7 +56,7 @@ jobs:
           else
             CHANGED=$(git diff --name-only ${{ github.event.pull_request.base.sha }} ${{ github.event.pull_request.head.sha }})
           fi
-          if echo "$CHANGED" | grep -q '^backend/'; then
+          if echo "$CHANGED" | grep -Eq '^(backend/|\.github/workflows/ci\.yml$)'; then
             echo "backend=true" >> "$GITHUB_OUTPUT"
           fi
       - uses: actions/setup-python@v5
@@ -65,12 +65,18 @@ jobs:
           python-version: "3.13"
           cache: pip
           cache-dependency-path: backend/requirements-dev.txt
+      - name: Install backend dependencies
+        if: steps.changes.outputs.backend == 'true'
+        working-directory: backend
+        run: python -m pip install -r requirements-dev.txt ruff
+      - name: Run Ruff
+        if: steps.changes.outputs.backend == 'true'
+        working-directory: backend
+        run: python -m ruff check .
       - name: Run tests
         if: steps.changes.outputs.backend == 'true'
         working-directory: backend
-        run: |
-          pip install -r requirements-dev.txt
-          python -m pytest tests/ -v --cov=app --cov-report=term-missing
+        run: python -m pytest tests/ -v --cov=app --cov-report=term-missing
 
   frontend-lint:
     name: Frontend Lint & Typecheck