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/data/repositories/auth_repository.ts

@@ -123,16 +123,31 @@ export class AuthRepository implements IAuthRepository {
    * 成功后写 guest token + deviceId + userId。
    */
   async guestLogin(deviceId: string): Promise<Result<GuestLoginResponse>> {
+    console.log("[AuthRepository.guestLogin] API call START", {
+      deviceIdLength: deviceId.length,
+      deviceIdPrefix: deviceId.slice(0, 8),
+    });
     return Result.wrap(async () => {
       const response = await this.api.guestLogin(
         GuestLoginRequest.from({ deviceId }),
       );
+      console.log("[AuthRepository.guestLogin] API call SUCCESS (Zod parsed)", {
+        hasToken: !!response.token,
+        hasUser: !!response.user,
+        userLastMessageAt: response.user?.lastMessageAt,
+      });
       await this.storage.setGuestToken(response.token);
       await this.storage.setDeviceId(deviceId);
       if (response.userId) {
         await this.userStorage.setUserId(response.userId);
       }
       return response;
+    }).catch((e) => {
+      console.error("[AuthRepository.guestLogin] API call FAILED", {
+        errorName: e?.name,
+        errorMessage: e?.message,
+      });
+      return Result.err(e);
     });
   }