refactor(chat): extract XState actors into chat-machine.actors.ts

- Split chat state machine actors (chatInit, sendMessageHttp, loadMoreHistory, chatWebSocket) into a dedicated module
- Add comprehensive console logging across the chat state machine for full trace debugging
- Comment out margin on text bubble CSS for layout adjustment
- Add debug logging to chat input bar send handler
- Clean up redundant comments in auth-screen component

src/app/auth/components/auth-screen.tsx

@@ -18,11 +18,6 @@ import { AuthBackground } from "./auth-background";
 import { AuthPanel } from "./auth-panel";
 
 export function AuthScreen() {
-  // ===== 鉴权路由跳转已由 src/router/proxy.ts 集中处理 =====
-  // 本组件只负责：
-  //   1. 渲染登录 UI
-  //   2. 邮箱登录成功 → 初始化 user store + navigate 到 /chat（业务层动作）
-
   const state = useAuthState();
   const authDispatch = useAuthDispatch();
   const userDispatch = useUserDispatch();