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/anisette-libcurl-init.ts

@@ -1,26 +1,41 @@
-import { loadLibcurl, libcurl } from "./wasm/libcurl"
+import { loadLibcurl, libcurl } from './wasm/libcurl';
 
-let initialized = false
-let initPromise: Promise<void> | null = null
+let initialized = false;
+let initPromise: Promise<void> | null = null;
 
 export async function initLibcurl(): Promise<void> {
   if (initialized) {
-    return
+    return;
   }
   if (initPromise) {
-    return initPromise
+    return initPromise;
   }
 
   initPromise = (async () => {
-    const loadedLibcurl = await loadLibcurl()
-    const wsProto = location.protocol === "https:" ? "wss:" : "ws:"
-    const wsUrl = `${wsProto}//${location.host}/wisp/`
-    loadedLibcurl.set_websocket(wsUrl)
-    await loadedLibcurl.load_wasm()
-    initialized = true
-  })()
+    let loadedLibcurl;
+    try {
+      loadedLibcurl = await loadLibcurl();
+    } catch (error) {
+      initPromise = null;
+      throw new Error(`Failed to load libcurl WASM module. ${error instanceof Error ? error.message : String(error)}`);
+    }
+    const wsProto = location.protocol === 'https:' ? 'wss:' : 'ws:';
+    const wsUrl = `${wsProto}//${location.host}/wisp/`;
+    loadedLibcurl.set_websocket(wsUrl);
+    try {
+      await loadedLibcurl.load_wasm();
+    } catch (error) {
+      initPromise = null;
+      throw new Error(
+        `Failed to initialize libcurl (is the WISP backend running?). ${
+          error instanceof Error ? error.message : String(error)
+        }`,
+      );
+    }
+    initialized = true;
+  })();
 
-  return initPromise
+  return initPromise;
 }
 
-export { libcurl }
+export { libcurl };