fix(ci): install webkit browser for Playwright E2E tests

Playwright config defaults to E2E_MODE='fast' which runs WebKit-only tests,
but CI was installing chromium. This caused all 419 tests to fail immediately
since the required browser wasn't available.

Changed CI to install webkit to match the default test configuration.

Author: pythoninthegrass

.github/workflows/test.yml

@@ -30,7 +30,7 @@ jobs:
         run: npm ci
 
       - name: Install Playwright browsers
-        run: npx playwright install --with-deps chromium
+        run: npx playwright install --with-deps webkit
 
       - name: Run Playwright tests
         working-directory: ./app/frontend