Separate CI job for functional tests

.github/workflows/main.yml

@@ -30,6 +30,19 @@ jobs:
           install-just: true
       - name: Set default environment variables
         run: cp dotenv-sample .env
-      - name: Run tests
-        run: |
-          just test-all
+      - name: Run tests (excluding functional)
+        run: just test-all
+
+  test-functional:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: "opensafely-core/setup-action@v1"
+        with:
+          python-version: "3.11"
+          install-just: true
+      - name: Install playwright browsers with dependencies
+        run: just playwright-install --with-deps
+      - name: Run functional tests
+        run: just test-functional