refactor: 重构解决方案相关Mapper

- 空值处理与类型控制：为关系型字段添加空值处理与类型控制逻辑
- 目录结构调整：分离SolutionList与Solution相关的Mapper为不同的文件

server/services/cms/solutionService.ts

@@ -1,7 +1,5 @@
-import {
-  toSolutionView,
-  toSolutionListView,
-} from '~~/server/mappers/solutionMapper';
+import { toSolutionView } from '~~/server/mappers/solutionMapper';
+import { toSolutionListView } from '~~/server/mappers/solutionListMapper';
 
 export const solutionService = {
   async getSolutionList(locale: string) {