Install Playwright before the Docker workflow's tests

Its test job runs the whole suite, browser tests included.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V9NnLxnPp8vaaurb3Z1MFy

.github/workflows/docker.yml

@@ -54,6 +54,9 @@ jobs:
       - name: Build Assets
         run: npm run build
 
+      - name: Install Playwright Browsers
+        run: npx playwright install --with-deps chromium
+
       - name: Run Tests
         run: ./vendor/bin/pest