feat: Add Flutter Code Check workflow

frontend/.github/workflows/flutter-check.yml

@@ -0,0 +1,34 @@
+name: Flutter Code Check
+
+on:
+  push:
+    branches: [main, dev, feature/*, hotfix]
+  pull_request:
+    branches: [main, dev]
+
+jobs:
+  flutter-check:
+    name: Analyse & Test Flutter
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: ⬇️ Checkout code
+        uses: actions/checkout@v3
+
+      - name: 💡 Set up Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          flutter-version: '3.19.0'  # ou celle que tu utilises
+          channel: stable
+
+      - name: 📦 Install dependencies
+        run: flutter pub get
+
+      - name: 🔍 Dart Analyzer
+        run: flutter analyze
+
+      # - name: 🧪 Run tests (if present)
+      #   run: flutter test || echo "No tests found"
+
+      - name: 🧱 Build (Flutter Web)
+        run: flutter build web --release