fix: SlackApiService RestTemplate 타임아웃 설정

src/main/java/DGU_AI_LAB/admin_be/domain/alarm/service/SlackApiService.java

@@ -8,6 +8,7 @@
 import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.http.*;
 import org.springframework.stereotype.Service;
+import org.springframework.http.client.SimpleClientHttpRequestFactory;
 import org.springframework.web.client.RestTemplate;
 
 import java.time.Duration;
@@ -28,7 +29,14 @@ public class SlackApiService {
     @Value("${slack.bot-token}")
     private String botToken;
 
-    private final RestTemplate restTemplate = new RestTemplate();
+    private final RestTemplate restTemplate = createRestTemplate();
+
+    private static RestTemplate createRestTemplate() {
+        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
+        factory.setConnectTimeout(3_000);
+        factory.setReadTimeout(5_000);
+        return new RestTemplate(factory);
+    }
     private final RedisTemplate<String, Object> redisTemplate;
 
     private static final String SLACK_USERS_CACHE_KEY = "slack:cache:users:list";