서버 코드를 Router, Service, Repository 계층으로 분리하고 오류 처리 및 파일 삭제 로직 개선

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/lib/server/services/index.ts

@@ -0,0 +1,10 @@
+export * as AuthService from "./auth";
+export * as CategoryService from "./category";
+export * as ClientService from "./client";
+export * as DirectoryService from "./directory";
+export * as FileService from "./file";
+export * as FileDeletionService from "./fileDeletion";
+export * as KeyService from "./key";
+export * as SearchService from "./search";
+export * as UploadService from "./upload";
+export * as UserService from "./user";