feat(kook): P2 KOOK 专属页+后端 admin 端点(design/17 §2/§4)

后端(KOOK REST, 复用 httpclient WithAuthScheme(Bot), token不打印):
- kook/admin.go(新): ListFriends/HandleFriendRequest/DeleteFriend/BlockFriend/
  ListUserChats/CreateUserChat/ListDirectMessages
- kook/admin_guild.go(新): ListGuilds/ListGuildChannels/ListGuildUsers/ListChannelMsgs/SendTestMessage
- gateway/admin_channels_platform.go(新): kookAdmin(反射解包namedAdapter命中内嵌PlatformAdapter)
  + 4 handler + adminKookView聚合(子项失败记errors不伪造)
- server.go 注册 4 条 ownerAuth 路由: /view /friends /friend/handle /message/test
- admin.go/admin_write_channel_config.go: AdminChannelAccount 加 Capabilities
前端(KOOK 专属页):
- KookPanel.tsx(新): 好友&申请/服务器/频道/成员/私信会话/发消息测试卡片
- AdapterDetailPage.tsx: platform==='kook' 渲染 KookPanel, 否则通用
- types.ts/api.ts: KOOK 类型 + adminChannelPlatformView/Friends/FriendHandle/MessageTest
文档: Docs/api-client.md 新增4端点契约(owner-only)+capabilities+v0.17
验收: go build/vet/test ./... 全绿 + npm run build 97模块全绿; 零新依赖
注: api.ts/types.ts 集中契约文件>500行属既有结构(未新增违规); KOOK其余REST方法留能力面待用

internal/services/gateway/admin.go

@@ -198,7 +198,9 @@ func (s *Server) maskedChannelAccounts() map[string][]AdminChannelAccount {
 			if !configuredAccount(a) {
 				continue
 			}
-			list = append(list, adminChannelAccountOf(runtimeconfig.Masked(a)))
+			account := adminChannelAccountOf(runtimeconfig.Masked(a))
+			account.Capabilities = platformAdminOps(platform)
+			list = append(list, account)
 		}
 		if len(list) > 0 {
 			out[platform] = list
@@ -207,6 +209,16 @@ func (s *Server) maskedChannelAccounts() map[string][]AdminChannelAccount {
 	return out
 }
 
+// platformAdminOps returns the account-level admin operations the platform's
+// adapter exposes, so the panel renders only the capabilities the account really
+// has. Platforms without a specialized adapter surface return nil (omitted).
+func platformAdminOps(platform string) []string {
+	if channelBasePlatform(platform) == "kook" {
+		return []string{"friends", "user_chats", "channels", "guilds", "message_test"}
+	}
+	return nil
+}
+
 // hasChannelSummary reports whether out already contains a summary for platform
 // (so a platform with a registered adapter is not duplicated).
 func (s *Server) hasChannelSummary(out []ChannelSummary, platform string) bool {