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

package.json

@@ -17,6 +17,8 @@
     "fix:prettier": "prettier --write .",
     "typecheck": "tsc --noEmit",
     "test": "node --import tsx --test $(find src -name '*.test.ts')",
+    "test:e2e": "playwright test",
+    "test:e2e:install": "playwright install chromium",
     "prepare": "husky",
     "commit": "git-cz",
     "postinstall": "node scripts/patch-folds.mjs",
@@ -106,6 +108,7 @@
   },
   "devDependencies": {
     "@lotusguild/element-call-embedded": "0.25.0-lotus.1",
+    "@playwright/test": "1.63.0",
     "@rollup/plugin-inject": "5.0.5",
     "@rollup/plugin-wasm": "6.2.2",
     "@types/chroma-js": "3.1.2",