Add a browser E2E project under tests/e2e/ that runs against a live panel
(there is no built-in server). Verified green (7/7) against a canary instance.
- playwright.config.ts: loads tests/e2e/.env (dotenv); a `setup` project logs in
once (auth.setup.ts — form #username/#password/#login_button -> ./login) and
stores the session, the chromium project reuses it via storageState. baseURL is
normalized to a trailing slash so relative gotos keep the access-code segment.
- Smoke specs: shell renders (sidebar/navbar, server-stamped data-bs-theme);
Dashboard group + Home link; six stat tiles + a live ./api?action=stats 200;
charts + server selector; customizer theme change persists across reload and
reset (opening the customizer panel) clears it.
- Config via env: XC_E2E_BASE_URL (admin base incl. access code), XC_E2E_USER,
XC_E2E_PASS (see .env.example / README). Makefile: `make e2e` / `e2e-ui` /
`e2e-install`. node_modules/.auth/results/.env gitignored; @playwright/test
pinned ~1.49 (Node 18+).
