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/src/components/LoginModal.tsx

@@ -0,0 +1,106 @@
+import type { ChangeEvent } from 'react';
+import { Button } from './ui/Button';
+import { Field } from './ui/Field';
+
+interface LoginModalProps {
+  open: boolean;
+  onClose: () => void;
+  appleId: string;
+  password: string;
+  busyLoginSign: boolean;
+  canSubmit: boolean;
+  onAppleIdChange: (value: string) => void;
+  onAppleIdBlur: () => void;
+  onPasswordChange: (value: string) => void;
+  onSubmit: () => void;
+}
+
+export function LoginModal({
+  open,
+  onClose,
+  appleId,
+  password,
+  busyLoginSign,
+  canSubmit,
+  onAppleIdChange,
+  onAppleIdBlur,
+  onPasswordChange,
+  onSubmit,
+}: LoginModalProps) {
+  if (!open) return null;
+
+  return (
+    <div className="fixed inset-0 z-50 flex items-start justify-center overflow-y-auto bg-black/30 backdrop-blur-sm p-4 pt-[8vh]">
+      <div className="w-full max-w-[440px] rounded-2xl border border-border bg-bg p-6 shadow-2xl anim-in">
+        <div className="mb-5 flex items-center justify-between">
+          <h2 className="text-[18px] font-semibold tracking-tight text-ink">Add Account</h2>
+          <button
+            type="button"
+            onClick={onClose}
+            disabled={busyLoginSign}
+            className="flex h-7 w-7 items-center justify-center rounded-full text-muted transition-colors hover:bg-surface hover:text-ink disabled:opacity-40"
+          >
+            <svg
+              className="h-4 w-4"
+              viewBox="0 0 16 16"
+              fill="none"
+              stroke="currentColor"
+              strokeWidth="1.5"
+              strokeLinecap="round"
+            >
+              <path d="M4 4l8 8M12 4l-8 8" />
+            </svg>
+          </button>
+        </div>
+
+        <div className="space-y-4">
+          <Field
+            label="Apple ID"
+            type="email"
+            autoComplete="username"
+            placeholder="you@icloud.com"
+            value={appleId}
+            onChange={(e: ChangeEvent<HTMLInputElement>) => onAppleIdChange(e.target.value)}
+            onBlur={onAppleIdBlur}
+          />
+          <Field
+            label="Password"
+            type="password"
+            autoComplete="current-password"
+            placeholder="Apple ID password"
+            value={password}
+            onChange={(e: ChangeEvent<HTMLInputElement>) => onPasswordChange(e.target.value)}
+            onKeyDown={(e) => {
+              if (e.key === 'Enter' && canSubmit && !busyLoginSign) {
+                e.preventDefault();
+                onSubmit();
+              }
+            }}
+          />
+        </div>
+
+        <div className="mt-4 space-y-1">
+          <p className="text-[11.5px] text-muted">
+            Your credentials are stored locally in this browser and are sent directly to Apple.
+          </p>
+          <p className="text-[11.5px] text-[var(--color-danger)] underline underline-offset-2 decoration-[var(--color-danger)]/40">
+            Verify that you trust the server hosting this page. A compromised server can intercept your credentials.
+          </p>
+        </div>
+
+        <div className="mt-5 flex justify-end">
+          <Button
+            variant="primary"
+            busy={busyLoginSign}
+            busyLabel="Signing In…"
+            disabled={!canSubmit}
+            onClick={onSubmit}
+            className="min-w-[140px]"
+          >
+            Sign In
+          </Button>
+        </div>
+      </div>
+    </div>
+  );
+}