test(e2e): Playwright smoke test — boot tier always, E2EE composer tier with credentials

Boot tier (runs against vite preview of dist/): login screen renders with
no page or console errors, sw.js is served and registers, the bundled
Element Call mounts in a frame with no failed asset requests. E2EE tier
(skipped without E2E_HOMESERVER/E2E_USER/E2E_PASSWORD): password login,
create an encrypted room, send text, attach a compressed JPEG, and assert
at the network level that every send is m.room.encrypted with no
plaintext body/url/file — the regression test #6/#7/#11 lacked.
Secrets and local usage documented in LOTUS_TESTING.md.

Fixes #90

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

playwright.config.ts

@@ -0,0 +1,35 @@
+import { defineConfig, devices } from '@playwright/test';
+
+// Playwright smoke tests (Gitea #90). Two tiers live under e2e/:
+//   - boot.spec.ts           always runs; serves the built dist/ via `vite preview`
+//                            and checks the client actually boots in a real browser.
+//   - e2ee-composer.spec.ts  skips itself unless E2E_HOMESERVER/E2E_USER/E2E_PASSWORD
+//                            are set (CI secrets — see LOTUS_TESTING.md).
+// `npm run build` must have produced dist/ before `npm run test:e2e`.
+const PORT = 4173;
+const BASE_URL = `http://localhost:${PORT}/`;
+
+export default defineConfig({
+  testDir: './e2e',
+  timeout: 60_000,
+  expect: { timeout: 15_000 },
+  fullyParallel: false,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 1 : 0,
+  workers: 1,
+  reporter: process.env.CI ? [['list'], ['html', { open: 'never' }]] : [['list']],
+  outputDir: 'test-results',
+  use: {
+    baseURL: BASE_URL,
+    screenshot: 'only-on-failure',
+    trace: 'retain-on-failure',
+    ...devices['Desktop Chrome'],
+  },
+  projects: [{ name: 'chromium', use: { ...devices['Desktop Chrome'] } }],
+  webServer: {
+    command: `npx vite preview --port ${PORT} --strictPort`,
+    url: BASE_URL,
+    reuseExistingServer: !process.env.CI,
+    timeout: 60_000,
+  },
+});