fix(auth): surface validation errors in email login/register forms

Validation failure was previously silent — the form's submit() returned
without dispatching or showing anything on screen, so users could not tell
why the login/register button appeared to do nothing.

Changes:
- Add validationError local state in EmailLoginForm and EmailRegisterForm
- Display first validation error via AuthErrorMessage, prioritised over
  the server's globalError (validation errors feel more immediate)
- Clear validation error on field change (standard "error fades as you
  fix it" UX) — implemented as onChange handlers, not useEffect, to
  avoid React's cascading-render anti-pattern
- Add observability to the entire email flow (was previously silent end
  to end): form submit ENTRY, validator rejection, actor ENTRY, actor
  DONE — mirrors the logging style already used by guestLoginActor
- Add entry: assign({ errorMessage: null }) to loadingEmailLogin and
  loadingEmailRegister so stale errors clear on transition into the
  loading state (matches loadingGuestLogin)

src/stores/auth/auth-actors.ts

@@ -25,8 +25,22 @@ const authRepo: IAuthRepository = authRepository;
 
 export const emailLoginActor = fromPromise<LoginStatus, { email: string; password: string }>(
   async ({ input }) => {
+    console.log("[auth-machine] emailLoginActor ENTRY", {
+      emailLength: input.email.length,
+      emailPreview: input.email.slice(0, 8),
+      passwordLength: input.password.length,
+    });
     const guestId = await readGuestId();
+    console.log("[auth-machine] emailLoginActor calling authRepo.emailLogin", {
+      hasGuestId: !!guestId,
+    });
     const result = await authRepo.emailLogin({ ...input, guestId });
+    console.log("[auth-machine] emailLoginActor authRepo.emailLogin DONE", {
+      success: result.success,
+      hasData: result.success ? !!result.data : null,
+      errorName: result.success ? null : result.error?.name,
+      errorMessage: result.success ? null : result.error?.message,
+    });
     if (Result.isErr(result)) throw result.error;
     return "email" as LoginStatus;
   },
@@ -36,17 +50,40 @@ export const emailRegisterThenLoginActor = fromPromise<
   LoginStatus,
   { email: string; password: string; username: string; confirmPassword: string }
 >(async ({ input }) => {
+  console.log("[auth-machine] emailRegisterThenLoginActor ENTRY", {
+    emailLength: input.email.length,
+    usernameLength: input.username.length,
+    passwordLength: input.password.length,
+    confirmPasswordLength: input.confirmPassword.length,
+  });
   const guestId = await readGuestId();
 
+  console.log("[auth-machine] emailRegisterThenLoginActor calling authRepo.register");
   const registerResult = await authRepo.register({ ...input, guestId });
+  console.log("[auth-machine] emailRegisterThenLoginActor authRepo.register DONE", {
+    success: registerResult.success,
+    errorName: registerResult.success ? null : registerResult.error?.name,
+    errorMessage: registerResult.success ? null : registerResult.error?.message,
+  });
   if (Result.isErr(registerResult)) throw registerResult.error;
 
   // 注册后自动登录（对齐 Dart 行为）
+  console.log(
+    "[auth-machine] emailRegisterThenLoginActor calling authRepo.emailLogin (post-register)",
+  );
   const loginResult = await authRepo.emailLogin({
     email: input.email,
     password: input.password,
     guestId,
   });
+  console.log(
+    "[auth-machine] emailRegisterThenLoginActor authRepo.emailLogin DONE",
+    {
+      success: loginResult.success,
+      errorName: loginResult.success ? null : loginResult.error?.name,
+      errorMessage: loginResult.success ? null : loginResult.error?.message,
+    },
+  );
   if (Result.isErr(loginResult)) throw loginResult.error;
   return "email" as LoginStatus;
 });