feat: add GitHub Actions workflow for frontend formatting and linting

.github/workflows/frontend-format.yml

@@ -0,0 +1,40 @@
+name: Frontend Format
+
+on:
+    pull_request:
+        paths:
+            - "frontend/**"
+            - "scripts/**"
+            - ".github/workflows/frontend-format.yml"
+
+jobs:
+    format:
+        runs-on: ubuntu-latest
+
+        steps:
+            - name: Check out repository
+              uses: actions/checkout@v4
+
+            - name: Set up Node.js
+              uses: actions/setup-node@v4
+              with:
+                  node-version: "20"
+
+            - name: Install dependencies
+              working-directory: frontend
+              run: npm install
+
+            - name: Run Prettier
+              working-directory: frontend
+              run: npm run format -- --check
+
+            - name: Run ESLint (fix mode)
+              working-directory: frontend
+              run: npm run lint -- --fix
+
+            - name: Upload formatting diff
+              if: failure()
+              uses: actions/upload-artifact@v4
+              with:
+                  name: frontend-formatting-diff
+                  path: frontend