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>

playwright.config.js

@@ -0,0 +1,18 @@
+// Real-browser tests: a production build of the app on its own port with a throwaway database, driven in Chrome.
+// Run with `npm run test:e2e`. It uses the Chrome already on this computer (no browser download).
+import { defineConfig } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './e2e',
+  timeout: 60_000,
+  expect: { timeout: 10_000 },
+  fullyParallel: false,
+  workers: 1,
+  reporter: [['list']],
+  use: { baseURL: 'http://localhost:3101', channel: 'chrome', trace: 'retain-on-failure' },
+  webServer: { command: 'bash e2e/start-server.sh', url: 'http://localhost:3101/', timeout: 120_000, reuseExistingServer: false },
+  projects: [
+    { name: 'setup', testMatch: /auth\.setup\.js/ },
+    { name: 'chrome', testMatch: /.*\.spec\.js/, dependencies: ['setup'], use: { storageState: 'e2e/.auth.json' } },
+  ],
+});