feat(web)!: sign in before joining a space and drop the stranger option

Opening a space link while signed out shows the sign-in page first and keeps
the link in memory. The channel settings no longer offer the stranger switch,
and the client supports API contract major 8.

web/src/lib/sender.ts

@@ -1,8 +1,8 @@
 import type { SenderInfo } from '@/core-bridge/types';
 
-/** 没有账号归属的内容(未登录访客)的显示名;设备只是账号的属性,不作为发送者展示 */
-export const GUEST_LABEL = '访客';
+/** 找不到作者信息时的显示名(频道只有登录账号,正常不会用到);设备只是账号的属性,不作为发送者展示 */
+export const UNKNOWN_SENDER_LABEL = '未知成员';
 
-export function senderLabel(source: { author?: SenderInfo } | undefined, fallback = GUEST_LABEL): string {
+export function senderLabel(source: { author?: SenderInfo } | undefined, fallback = UNKNOWN_SENDER_LABEL): string {
   return source?.author?.displayName || source?.author?.username || fallback;
 }