Real-browser tests (Playwright) and housekeeping

- npm run test:e2e builds the app, runs it on port 3101 with an empty throwaway
  database and drives Chrome (the installed one; no browser download) through
  notes and the paste check, the daily five minutes and weekly recall,
  translation compare (Bible text faked), and two-screen presenting.
- Vitest skips e2e/; ESLint knows the e2e folder and playwright.config.js.
- .gitignore: the local demo video, Playwright output and sign-in file.
- README and TODO describe the browser tests and what CI still needs.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

TODO.md

@@ -9,8 +9,9 @@ Ideas for the app that haven't been built yet, roughly in the order I'd do them.
       "sign out other devices"; optionally a login alert through ntfy.
 - [x] **Server health page for the admin.** Last backup, disk use, failed notifications, recent sign-in failures, and a
       "restore a snapshot" button (snapshots already exist under `DATA_DIR/backups`).
-- [ ] **Checks on every push.** Run tests and lint on the Gitea server, plus a few real-browser tests (Playwright) for sign-in,
-      creating a study and syncing; so far everything is tested in simulation.
+- [ ] **Checks on every push.** Run `npm run test:run`, `npm run lint` and `npm run test:e2e` on the Gitea server for every push.
+      The real-browser tests now exist (`e2e/`, run by hand); what's left is running them automatically, and adding sign-in
+      and cross-device sync to them.
 - [x] **Split `server/index.js`** into one file per area (`server/routes/`: auth, account, projects, reader, sharing, admin).
 
 ## Teaching together