feat(demo): add Playwright browser tests, fix Homepage config mount

- Add Playwright E2E test suite covering all 13 user-facing services
- Fix Homepage HTTP 500 by removing read-only bind mount (:ro) so it
  can create its required logs/ directory
- Pin @playwright/test to exact 1.52.0 to match Docker image browsers
- Add .gitignore entries for auto-generated Homepage files and
  Playwright artifacts
- All 13 Playwright tests passing (Chromium headless)

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

.gitignore

@@ -19,3 +19,12 @@ Thumbs.db
 *.tmp
 *.bak
 tmp_template.yml
+
+# Homepage auto-generated files
+demo/config/homepage/logs/
+demo/config/homepage/kubernetes.yaml
+
+# Playwright
+node_modules/
+test-results/
+package-lock.json