项目快照按渠道分区，后台项目工程支持渠道筛选与游标分页

项目快照对象键升级为 agc/project-snapshots/v2/{channel}/{user}/{project}/，渠道取部署配置 GENARRATIVE_AGC_PROJECT_SNAPSHOT_CHANNEL（缺省沿用客户端下载渠道），非法渠道在写入处失败关闭
后台新增渠道列表接口，项目工程列表与下载接受 channel，游标绑定渠道并拒绝跨渠道复用
后台项目工程用户列改为素材查询口径：昵称 + 陶泥号 + 用户详情入口，由 api-server 解析作者信息
后台项目工程改为游标分页：每页 20/50/100、上一页/下一页与当前页提示，翻页失败保留当前页
部署环境示例补充快照渠道配置，并同步运维、技术方案、里程碑与决策记录文档

apps/admin-web/src/api/adminApiClient.ts

@@ -34,6 +34,7 @@ import type {
   AdminLoginResponse,
   AdminMeResponse,
   AdminOverviewResponse,
+  AdminProjectSnapshotChannelsResponse,
   AdminProjectSnapshotListQuery,
   AdminProjectSnapshotListResponse,
   AdminRechargeOrderListQuery,
@@ -214,6 +215,7 @@ export function listAdminProjectSnapshots(
 ) {
   const params = new URLSearchParams();
   if (query.cursor) params.set('cursor', query.cursor);
+  if (query.channel) params.set('channel', query.channel);
   params.set('limit', String(query.limit ?? 20));
   return request<AdminProjectSnapshotListResponse>(
     `/admin/api/project-snapshots?${params.toString()}`,
@@ -221,13 +223,27 @@ export function listAdminProjectSnapshots(
   );
 }
 
+export function getAdminProjectSnapshotChannels(
+  token: string,
+  signal?: AbortSignal,
+) {
+  return request<AdminProjectSnapshotChannelsResponse>(
+    '/admin/api/project-snapshots/channels',
+    { token, signal },
+  );
+}
+
 export async function downloadAdminProjectSnapshot(
   token: string,
+  channel: string,
   userId: string,
   projectId: string,
   signal?: AbortSignal,
 ) {
-  const path = `/admin/api/project-snapshots/${encodeURIComponent(userId)}/${encodeURIComponent(projectId)}/download`;
+  const params = new URLSearchParams();
+  if (channel) params.set('channel', channel);
+  const query = params.toString();
+  const path = `/admin/api/project-snapshots/${encodeURIComponent(userId)}/${encodeURIComponent(projectId)}/download${query ? `?${query}` : ''}`;
   const response = await fetch(buildRequestUrl(path), {
     headers: {
       Authorization: `Bearer ${token.trim()}`,