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>

demo/docker-compose.yml.template

@@ -92,8 +92,7 @@ services:
     ports:
       - "${HOMEPAGE_PORT}:3000"
     volumes:
-      - ${COMPOSE_PROJECT_NAME}_homepage_data:/app/config
-      - ./config/homepage:/app/config/default:ro
+      - ./config/homepage:/app/config
     environment:
       - PUID=${DEMO_UID}
       - PGID=${DEMO_GID}