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/lib/services/admin/cache.service.ts

@@ -0,0 +1,18 @@
+import {BaseService} from '@/lib/services/core';
+import type {CacheConfig, CacheStatus} from './types';
+
+export class AdminCacheService extends BaseService {
+  protected static readonly basePath = '/api/v1/admin';
+
+  static async getCacheStatus(): Promise<CacheStatus> {
+    return this.get<CacheStatus>('/cache/status');
+  }
+
+  static async updateCacheConfig(config: CacheConfig): Promise<void> {
+    return this.post<void>('/cache/config', config);
+  }
+
+  static async clearCache(): Promise<void> {
+    return this.post<void>('/cache/clear');
+  }
+}