chore: Rename group_1 to biz_core in remaining files

src/main/java/io/shinhanlife/axhub/biz/mcp/tool/annotation/McpTool.java

@@ -15,6 +15,6 @@ public @interface McpTool {
 
     String name();
     String description();
-    String group() default "group_1";
+    String group() default "biz_core";
     String routingType() default "HTTP";
 }

src/main/java/io/shinhanlife/axhub/biz/mcp/tool/service/CommonUtilityService.java

@@ -10,7 +10,7 @@ import io.shinhanlife.axhub.biz.mcp.tool.dto.EmailSendReq;
 @McpTool(
     name = "common_utility_tool", 
     description = "전사 공통 유틸리티 툴 (HR 및 알림)", 
-    group = "group_1", 
+    group = "biz_core", 
     routingType = "HTTP"
 )
 public class CommonUtilityService extends AbstractMcpToolService {