fix(kakao): Kakao SDK v2 authorize 방식으로 전환 + code 교환 엔드포인트

- Kakao SDK v2.7에서 Auth.login() 제거 → authorize() 리다이렉트 플로우 사용
- services/kakao.ts: kakaoWebLoginStart() redirect 시작
- RootNavigator: 웹 URL의 code + state=kakao_login 감지 → kakaoCodeLogin 호출
- useAuthStore.kakaoCodeLogin 추가 (authApi.kakaoCode 호출)
- 백엔드 /auth/kakao/code: REST API 키로 code→access_token 교환 후 기존 processKakaoLogin 재사용
- api-secrets에 kakaoRestApiKey/kakaoClientSecret 슬롯 추가
- 환경변수: KAKAO_REST_API_KEY 서버에 저장 완료

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/src/routes/auth.ts

@@ -1,4 +1,4 @@
-import type { FastifyInstance } from 'fastify';
+import type { FastifyInstance, FastifyReply } from 'fastify';
 import bcrypt from 'bcrypt';
 import { z } from 'zod';
 
@@ -17,8 +17,10 @@ const LoginBody = z.object({
   password: z.string().min(1),
 });
 
-const KakaoBody = z.object({
-  accessToken: z.string().min(10),
+const KakaoBody = z.object({ accessToken: z.string().min(10) });
+const KakaoCodeBody = z.object({
+  code: z.string().min(5),
+  redirectUri: z.string().url(),
 });
 
 type KakaoMe = {
@@ -40,6 +42,62 @@ async function fetchKakaoProfile(accessToken: string): Promise<KakaoMe> {
   return (await res.json()) as KakaoMe;
 }
 
+async function exchangeKakaoCode(code: string, redirectUri: string): Promise<string> {
+  const restKey = process.env.KAKAO_REST_API_KEY;
+  if (!restKey) throw new Error('KAKAO_REST_API_KEY not configured');
+  const form = new URLSearchParams({
+    grant_type: 'authorization_code',
+    client_id: restKey,
+    redirect_uri: redirectUri,
+    code,
+  });
+  if (process.env.KAKAO_CLIENT_SECRET) {
+    form.set('client_secret', process.env.KAKAO_CLIENT_SECRET);
+  }
+  const res = await fetch('https://kauth.kakao.com/oauth/token', {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/x-www-form-urlencoded;charset=utf-8' },
+    body: form.toString(),
+  });
+  if (!res.ok) throw new Error(`Kakao token exchange ${res.status}: ${await res.text()}`);
+  const data = (await res.json()) as any;
+  return data.access_token as string;
+}
+
+async function processKakaoLogin(app: FastifyInstance, reply: FastifyReply, accessToken: string) {
+  let me: KakaoMe;
+  try {
+    me = await fetchKakaoProfile(accessToken);
+  } catch {
+    return reply.code(401).send({ message: '카카오 인증 실패' });
+  }
+  const kakaoId = String(me.id);
+  const email = me.kakao_account?.email;
+  const name = me.kakao_account?.profile?.nickname ?? me.properties?.nickname ?? '카카오사용자';
+  const profileImage = me.kakao_account?.profile?.profile_image_url ?? me.properties?.profile_image;
+
+  let user = await app.prisma.user.findUnique({
+    where: { kakaoId },
+    include: { profile: true },
+  });
+  if (!user) {
+    user = await app.prisma.user.create({
+      data: {
+        kakaoId,
+        email: email ?? null,
+        name,
+        phone: me.kakao_account?.phone_number,
+        provider: 'KAKAO',
+        profileImage,
+        profile: { create: { age: 30, gender: 'MALE', job: '기타' } },
+      },
+      include: { profile: true },
+    });
+  }
+  const token = await reply.jwtSign({ sub: user.id, email: user.email ?? undefined });
+  return { token, user: publicUser(user) };
+}
+
 export async function authRoutes(app: FastifyInstance) {
   app.post('/register', async (req, reply) => {
     const body = RegisterBody.parse(req.body);
@@ -54,13 +112,7 @@ export async function authRoutes(app: FastifyInstance) {
         name: body.name,
         phone: body.phone,
         provider: 'EMAIL',
-        profile: {
-          create: {
-            age: body.age,
-            gender: body.gender,
-            job: body.job ?? '기타',
-          },
-        },
+        profile: { create: { age: body.age, gender: body.gender, job: body.job ?? '기타' } },
       },
       include: { profile: true },
     });
@@ -86,46 +138,18 @@ export async function authRoutes(app: FastifyInstance) {
 
   app.post('/kakao', async (req, reply) => {
     const body = KakaoBody.parse(req.body);
-    let me: KakaoMe;
+    return processKakaoLogin(app, reply, body.accessToken);
+  });
+
+  app.post('/kakao/code', async (req, reply) => {
+    const body = KakaoCodeBody.parse(req.body);
+    let accessToken: string;
     try {
-      me = await fetchKakaoProfile(body.accessToken);
-    } catch (e) {
-      return reply.code(401).send({ message: '카카오 인증 실패' });
+      accessToken = await exchangeKakaoCode(body.code, body.redirectUri);
+    } catch (e: any) {
+      return reply.code(401).send({ message: `카카오 토큰 교환 실패: ${e?.message ?? ''}` });
     }
-
-    const kakaoId = String(me.id);
-    const email = me.kakao_account?.email;
-    const name = me.kakao_account?.profile?.nickname ?? me.properties?.nickname ?? '카카오사용자';
-    const profileImage = me.kakao_account?.profile?.profile_image_url ?? me.properties?.profile_image;
-
-    let user = await app.prisma.user.findUnique({
-      where: { kakaoId },
-      include: { profile: true },
-    });
-
-    if (!user) {
-      user = await app.prisma.user.create({
-        data: {
-          kakaoId,
-          email: email ?? null,
-          name,
-          phone: me.kakao_account?.phone_number,
-          provider: 'KAKAO',
-          profileImage,
-          profile: {
-            create: {
-              age: 30,
-              gender: 'MALE',
-              job: '기타',
-            },
-          },
-        },
-        include: { profile: true },
-      });
-    }
-
-    const token = await reply.jwtSign({ sub: user.id, email: user.email ?? undefined });
-    return { token, user: publicUser(user) };
+    return processKakaoLogin(app, reply, accessToken);
   });
 
   app.get('/me', { onRequest: [app.authenticate] }, async (req) => {