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>

package.json

@@ -15,7 +15,8 @@
     "coverage": "vitest run --coverage",
     "backup": "bash scripts/backup-data.sh",
     "restore": "bash scripts/restore-data.sh",
-    "lint": "eslint ."
+    "lint": "eslint .",
+    "test:e2e": "playwright test"
   },
   "dependencies": {
     "@simplewebauthn/browser": "^13.3.0",
@@ -37,6 +38,7 @@
   },
   "devDependencies": {
     "@eslint/js": "^10.0.1",
+    "@playwright/test": "^1.64.1",
     "@testing-library/jest-dom": "^6.9.1",
     "@testing-library/react": "^16.3.2",
     "@testing-library/user-event": "^14.6.1",