fix(lighthouse): set LHCI_CHROME_PATH via runtime discovery

- Re-add Playwright Chromium install (LHCI needs a Chrome binary)
- Use `find` at runtime to locate Playwright's chrome binary:
  CHROME_PATH=$(find /home/runner/.cache/ms-playwright -name chrome ...)
- Pass to LHCI via LHCI_CHROME_PATH env var so LHCI does
  not try (and fail) to auto-download Puppeteer's Chromium

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/ci.yml

@@ -71,10 +71,15 @@ jobs:
           cache: npm
       - run: npm ci
       - run: npm run build
+      - name: Install Chromium for Lighthouse
+        run: |
+          npm install -g playwright
+          npx playwright install chromium
       - name: Run Lighthouse CI
         run: |
+          CHROME_PATH=$(find /home/runner/.cache/ms-playwright -name chrome -type f 2>/dev/null | head -1)
           npm install -g @lhci/cli
-          lhci autorun
+          LHCI_CHROME_PATH="$CHROME_PATH" lhci autorun
 
   build-and-push:
     runs-on: runners-cartsnitch