fix: Apply npm ci workaround to e2e_tests workflow

The e2e_tests workflow was still using npm ci which fails due to the
npm optional dependencies bug (npm/cli#4828).
This applies the same workaround already used in main.yml.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: felixweinberger

.github/workflows/e2e_tests.yml

@@ -37,7 +37,9 @@ jobs:
             ${{ runner.os }}-playwright-
 
       - name: Install dependencies
-        run: npm ci
+        # Working around https://github.com/npm/cli/issues/4828
+        # run: npm ci
+        run: npm install --no-package-lock
 
       - name: Install Playwright dependencies
         run: npx playwright install-deps