fix(admin-chat-calculate): 캐릭터 정산 API

- ONLY_FULL_GROUP_BY 대응
- c2.image_path 집계식 적용

src/main/kotlin/kr/co/vividnext/sodalive/admin/chat/calculate/AdminChatCalculateQueryRepository.kt

@@ -51,9 +51,8 @@ class AdminChatCalculateQueryRepository(
         val c2 = QChatCharacter("c2")
 
         val characterIdExpr = c1.id.coalesce(c2.id)
-        // ONLY_FULL_GROUP_BY 대응: name/imagePath는 집계 함수로 선택
         val characterNameAgg = Expressions.stringTemplate(
-            "coalesce(max({0}), max({1}))",
+            "coalesce(max({0}), max({1}), '')",
             c1.name,
             c2.name
         )