chore(playground-server): Update checkstyle suppressions and config

Author: lzwjava

playground-server/.claude/settings.local.json

@@ -0,0 +1,9 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(mvn checkstyle:check:*)"
+    ],
+    "deny": [],
+    "ask": []
+  }
+}

playground-server/checkstyle-suppressions.xml

@@ -1,7 +1,7 @@
 <!DOCTYPE suppressions PUBLIC "-//Checkstyle//DTD Suppression DTD//EN" "https://checkstyle.org/dtds/suppressions_1_2.dtd">
 <suppressions>
     <suppress checks="MissingJavadocMethod" files=".*\.java" />
-    <suppress checks="HideUtilityClassConstructor" files="org/lzwjava/.*\.java"/>
-    <suppress checks="DesignForExtension" files="org/lzwjava/.*\.java"/>
-    <suppress checks="BanSystemOut" files="org/lzwjava/Application.java"/>
+    <suppress checks="HideUtilityClassConstructor" files="src/main/java/org/lzw/.*\.java"/>
+    <suppress checks="DesignForExtension" files="src/main/java/org/lzw/.*\.java"/>
+    <suppress checks="BanSystemOut" files="src/main/java/org/lzw/Application.java"/>
 </suppressions>

playground-server/src/main/java/org/lzw/Application.java

@@ -1,8 +1,13 @@
 package org.lzw;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 public class Application {
 
+    private static final Logger log = LoggerFactory.getLogger(Application.class);
+
     public static void main(String[] args) {
-        System.out.println("Application started without Spring Boot");
+        log.info("Application started without Spring Boot");
     }
 }