refactor(frontend): colocate admin components and split service layer

Move route-specific admin components from components/common/admin into
app/(main)/admin/<feature>/components/. Split AdminService god object into
domain services, fix UploadService to use BaseService, add AdminUploadService,
consolidate DB export into DbManageService, and migrate consumers to the
unified services entry.

frontend/hooks/use-public-config.ts

@@ -1,5 +1,5 @@
 import {useQuery} from '@tanstack/react-query'
-import {ConfigService} from '@/lib/services/config'
+import services from '@/lib/services'
 
 /**
  * 获取公共配置（使用 React Query 进行统一缓存与自动同步）
@@ -12,7 +12,7 @@ import {ConfigService} from '@/lib/services/config'
 export function usePublicConfig() {
   const { data: config, isLoading: loading, error } = useQuery({
     queryKey: ['public-config'],
-    queryFn: () => ConfigService.getPublicConfig(),
+    queryFn: () => services.config.getPublicConfig(),
     staleTime: 5 * 60 * 1000, // 5 分钟缓存
   })