chore(auth): add debug logging to guest login flow

Add console.log instrumentation across the guest login pipeline (auth-machine, authRepository, authApi) to trace request lifecycle and surface Zod parsing failures with detailed issue info. Useful for diagnosing lastMessageAt schema mismatches.

src/stores/auth/auth-machine.ts

@@ -120,16 +120,35 @@ const syncFacebookBackendActor = fromPromise<
 // 受保护 API 401 会由 HTTP 层清掉 token 回到 splash，无需在此处主动校验。
 
 const guestLoginActor = fromPromise<LoginStatus, void>(async () => {
+  console.log("[auth-machine] guestLoginActor ENTRY");
+
   // 1. 先查本地 guestToken —— 已有就直接进 idle（带 pendingRedirect）
   const hasTokenR = await AuthStorage.getInstance().hasGuestToken();
+  console.log("[auth-machine] guestLoginActor hasGuestToken", {
+    success: hasTokenR.success,
+    hasData: hasTokenR.success ? !!hasTokenR.data : null,
+  });
   if (hasTokenR.success && hasTokenR.data) {
+    console.log("[auth-machine] guestLoginActor SHORT-CIRCUIT (has local guestToken) → return guest");
     return "guest" as LoginStatus;
   }
   // Result.err(_) 时**不**抛 —— 落到 API 路径让真正的错误信号出现
 
   // 2. 没有（或读不出）才走完整流程：拿 deviceId → 调后端
   const deviceId = await deviceIdentifier.getDeviceId();
+  console.log("[auth-machine] guestLoginActor deviceId", {
+    length: deviceId.length,
+    prefix: deviceId.slice(0, 8),
+  });
+
+  console.log("[auth-machine] guestLoginActor calling authRepository.guestLogin");
   const result = await authRepository.guestLogin(deviceId);
+  console.log("[auth-machine] guestLoginActor authRepository.guestLogin 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 "guest" as LoginStatus;
 });