Add total activity count when merging members (#2854)

Signed-off-by: Sameh16 <sameh_mohamed16@hotmail.com>

Author: Sameh16

frontend/src/modules/member/components/member-merge-suggestions.vue

@@ -199,6 +199,7 @@ const preview = computed(() => {
     ...secondaryMember.identities,
   ];
   mergedMembers.score = Math.max(primaryMember.score, secondaryMember.score);
+  mergedMembers.activityCount = primaryMember.activityCount + secondaryMember.activityCount;
   return mergedMembers;
 });