[FIX] security 수정

Author: hyunbin1

src/main/java/com/example/ai_tutor/global/config/security/SecurityConfig.java

@@ -71,7 +71,7 @@ public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
                 .cors(cors -> cors.configurationSource(corsConfigurationSource()))
                 .csrf(AbstractHttpConfigurer::disable)
                 .httpBasic(AbstractHttpConfigurer::disable)
-                .sessionManagement(session -> session.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
+                .sessionManagement(session -> session.sessionCreationPolicy(SessionCreationPolicy.IF_REQUIRED))
                 .formLogin(AbstractHttpConfigurer::disable)
                 .exceptionHandling(exception -> exception.authenticationEntryPoint(new CustomAuthenticationEntryPoint()))
                 .authorizeHttpRequests(authorize -> authorize