fix(gateway): accept Kakao already-registered response

app/gateway-api/test/authFlow.test.ts

@@ -71,7 +71,9 @@ const buildCaller = (
             };
         },
         signup: async () =>
-            options.kakaoSignupAlreadyRegistered ? { msg: 'already registered' as const } : { id: kakaoProfile.id },
+            options.kakaoSignupAlreadyRegistered
+                ? { alreadyRegistered: true }
+                : { id: kakaoProfile.id, alreadyRegistered: false },
         getMe: async () => ({
             id: kakaoProfile.id,
             kakaoAccount: {

app/gateway-api/test/kakaoClient.test.ts

@@ -0,0 +1,47 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { KakaoOAuthClient } from '../src/auth/kakaoClient.js';
+
+const createClient = (): KakaoOAuthClient =>
+    new KakaoOAuthClient({
+        restKey: 'rest-key',
+        redirectUri: 'https://gateway.example.test/oauth/callback',
+        apiHost: 'https://kapi.example.test',
+    });
+
+describe('Kakao OAuth HTTP transport', () => {
+    afterEach(() => {
+        vi.restoreAllMocks();
+    });
+
+    it('normalizes Kakao -102 already registered errors into an account recovery result', async () => {
+        const fetchMock = vi.spyOn(globalThis, 'fetch').mockResolvedValueOnce(
+            new Response(JSON.stringify({ msg: 'already registered', code: -102 }), {
+                status: 400,
+                headers: { 'Content-Type': 'application/json' },
+            })
+        );
+
+        await expect(createClient().signup('access-token')).resolves.toEqual({
+            alreadyRegistered: true,
+        });
+        expect(fetchMock).toHaveBeenCalledWith(new URL('https://kapi.example.test/v1/user/signup'), {
+            headers: {
+                Authorization: 'Bearer access-token',
+            },
+        });
+    });
+
+    it('continues to reject unrelated Kakao signup errors', async () => {
+        vi.spyOn(globalThis, 'fetch').mockResolvedValueOnce(
+            new Response(JSON.stringify({ msg: 'invalid request', code: -201 }), {
+                status: 400,
+                headers: { 'Content-Type': 'application/json' },
+            })
+        );
+
+        await expect(createClient().signup('access-token')).rejects.toThrow(
+            'Kakao signup error: {"msg":"invalid request","code":-201}'
+        );
+    });
+});