feat(Volunteer): 봉사 시간, 봉사 횟수 업데이트 추가

Author: m-a-king

src/main/java/com/somemore/volunteer/domain/Volunteer.java

@@ -65,6 +65,11 @@ public void updateWith(VolunteerProfileUpdateRequestDto dto, String imgUrl) {
         this.imgUrl = imgUrl;
     }
 
+    public void updateVolunteerStats(int hours, int count) {
+        this.totalVolunteerHours += hours;
+        this.totalVolunteerCount += count;
+    }
+
     @Builder
     private Volunteer(
             OAuthProvider oauthProvider,