chore(backend): add github action for ruff

.github/workflows/lint-backend-style.yml

@@ -0,0 +1,19 @@
+name: Lint backend style
+
+on: [push, pull_request]
+
+jobs:
+  ruff:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: install Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: 3.12
+
+      - name: install ruff
+        run: pip install ruff
+
+      - name: ruff
+        run: python -m ruff check ./backend