refactor: migrate frontend to React + Tailwind, add Docker + tests

Replace the vanilla-TS innerHTML frontend with a type-checked React
component tree (React 19 + Tailwind v4 + Vite).

Frontend:
- 14 components: Header, Stepper, LoginPage, LoginModal, SignPage,
  DropZone, DevicePicker, ProgressCard, SavedAccountsList, TrustModal,
  TwoFactorModal, Button, Field, Chip, Modal
- lib/ extracts: storage (10 localStorage keys preserved), pair-record,
  account-session, log-parser, ids, use-log hook
- flows/ encapsulate async pair/login/sign/install with dependency injection
- Accounts page as main view with Add Account modal
- Fullscreen progress overlay during sign/install
- Account selector + device picker on Sign page
- Security notice in login modal (server trust warning)
- All addLog calls mirrored to console.log for devtools debugging

Build:
- bun run dev: submodule init + install + wasm dist + vite + wrangler
- bun run setup: one-shot project bootstrap
- Docker: multi-stage bun build → nginx on :3000
- build:wasm:dist copies pre-built src→dist (no Rust/Emscripten needed)
- jszip/node-forge/fflate pre-bundled for CJS→ESM conversion

Tests:
- 163 vitest tests (happy-dom): all lib, components, App integration,
  WASM dist artifact checks, libcurl Apple connectivity, anisette init
  error handling

Cleanup:
- Delete yarn.lock (bun.lock canonical), expand .gitignore
- Remove README.zh.md, rewrite README.md + AGENTS.md
- Update libcurl.js submodule to f65d440 (CI build artifacts)

frontend/package.json

@@ -7,7 +7,10 @@
     "dev": "vite",
     "build": "tsc && vite build",
     "serve": "vite preview",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "dependencies": {
     "@lbr77/anisette-js": "0.1.3",
@@ -17,13 +20,23 @@
     "jszip": "^3.10.1",
     "libcurl.js": "workspace:*",
     "node-forge": "^1.3.3",
+    "react": "^19.1.0",
+    "react-dom": "^19.1.0",
     "webmuxd": "workspace:*"
   },
   "devDependencies": {
     "@tailwindcss/vite": "^4.2.1",
+    "@testing-library/jest-dom": "^6.6.3",
+    "@testing-library/react": "^16.1.0",
+    "@testing-library/user-event": "^14.5.2",
+    "@types/react": "^19.1.0",
+    "@types/react-dom": "^19.1.0",
+    "@vitejs/plugin-react": "^4.4.0",
+    "happy-dom": "^15.11.7",
     "tailwindcss": "^4.2.1",
     "typescript": "~5.9.3",
-    "vite": "^7.3.1"
+    "vite": "^7.3.1",
+    "vitest": "^2.1.8"
   },
   "packageManager": "bun@1.3.11"
 }