fix(security): permitAll 패턴에서 /api/auth/me 제외

/api/auth/** 와일드카드가 /api/auth/me까지 공개하여
인증 없이 접근 시 NPE(500) 발생. /api/auth/google과
/api/auth/logout만 공개하도록 수정.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/java/com/gcsc/guide/config/SecurityConfig.java

@@ -41,7 +41,8 @@ public class SecurityConfig {
                 session.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
             .authorizeHttpRequests(auth -> auth
                 .requestMatchers(
-                    "/api/auth/**",
+                    "/api/auth/google",
+                    "/api/auth/logout",
                     "/api/health",
                     "/actuator/health",
                     "/h2-console/**",