修复已建立的P2P会话详情栏/头像404：话题名不是对方user_id

用户报告：控制台反复出现 GET /v1/im/users/p2pp77kUAkgqpVbZoiTpjPWtg/profile
404。根因：这个应用的多处代码（DetailColumn的好友资料/拉黑/备注/删除好友，以及
本会话早前刚加的头像peerProfileQuery）一直假设"P2P会话的topicId就是对方的
user_id"——这个假设只在"第一次用对方usr...地址打开、还从未真正subscribe过"
这个短暂窗口内成立。读tinode-sdk源码确认：一旦subscribe成功，SDK会把这个话题
从usr...地址重命名为服务端分配的真实p2p...哈希名，而Topic.topicType()自己的
前缀表里根本没有p2p这一项（只有usr映射到P2P类型），导致topic.isP2PType()/
topic.p2pPeerDesc()对已建立的会话恒定返回false/undefined——SDK自己内建的"取
对方身份"方法在这个场景下也是坏的，不只是这个项目自己的代码有问题。

只要一个P2P会话有过真实的消息历史（几乎所有现存对话都是这样），它的topicId
就是这个不能反解的p2p...哈希，而不是对方user_id，直接拿去查/v1/im/users/{id}/
profile、匹配好友列表的user_id、传给拉黑/删除好友接口，全部会用错id。

修复：topics.ts新增getP2PPeerUserId(topic, myUserId)——topicId本身是usr...
前缀时直接返回（还没subscribe过，本来就对），否则读topic.subscribers()真实
的订阅者列表，找出不是自己的那个人的真实user_id；订阅者列表还没加载出来时返回
undefined而不是猜一个不可能对的值，调用方原本就有的enabled门控会正确地等待
而不是提前拿错误id发请求。tinode-sdk.d.ts补充subscribers()方法和Subscription
类型声明（原来完全没声明这个方法）。DetailColumn.tsx/ConversationView.tsx改用
这个真实user_id去查资料/匹配好友/头像取色，不再直接假设topicId能用。

实机验证：真实会话grpMc5uN...不对，是p2pp77kUAkgqpVbZoiTpjPWtg（systest04↔
systest02，有真实历史消息的老会话）——修复前详情栏"ID:"整行空白、404貫穿控制
台；修复后详情栏正确显示"ID：usrp77kUAkgqpU"，好友资料/备注/拉黑状态全部正确
关联到真实好友记录。

web/src/features/messages/ConversationView.tsx

@@ -35,6 +35,7 @@ import {
   closeConversation,
   ensureTopicAttached,
   forgetTopic,
+  getP2PPeerUserId,
   markConfirmedRead,
   openConversation,
   setActiveConversationTopic,
@@ -463,16 +464,23 @@ export function ConversationView() {
   // `['me']` key NavRail/ChatListColumn/SettingsLayout already keep warm, so this is a cache read in
   // the normal case, not a new request.
   const meQuery = useQuery({ queryKey: ['me'], queryFn: getMe });
+  // NOT topicId -- see getP2PPeerUserId's own doc comment. A P2P topic with any real history is
+  // addressed by a real, opaque `p2p...` name, not the peer's `usr...` id (that only holds true in
+  // the brief window before the very first subscribe) -- confirmed live: without this, this query
+  // 404s (`GET /users/{p2p...}/profile`) for every established conversation, and only ever appeared
+  // to work in earlier testing because that test happened to use a conversation opened for the first
+  // time in the same session, before the SDK's own rename kicked in.
+  const peerUserId = !isGroup && !isSelf && topicId ? getP2PPeerUserId(tinode.getTopic(topicId), myUserId) : undefined;
   // Real gap this was written to close: the chat header/message-row avatars only ever drew the
   // letter-tile fallback, even after a real custom avatar was uploaded and correctly showing up on
   // the contacts pages (FriendProfileView/ContactsListColumn) -- those read this exact same REST
   // profile, the conversation screen just never fetched it. Same query DetailColumn already runs
-  // (`['user-profile', topicId]`), so this dedupes with it whenever the detail panel happens to be
+  // (`['user-profile', peerUserId]`), so this dedupes with it whenever the detail panel happens to be
   // open, and only fetches for a real P2P peer, never for a group or `slf`.
   const peerProfileQuery = useQuery({
-    queryKey: ['user-profile', topicId],
-    queryFn: () => getUserProfile(topicId || ''),
-    enabled: !!topicId && !isGroup && !isSelf,
+    queryKey: ['user-profile', peerUserId],
+    queryFn: () => getUserProfile(peerUserId || ''),
+    enabled: !!peerUserId,
   });
   const membersQuery = useQuery({
     queryKey: ['group-members', topicId],
@@ -525,6 +533,11 @@ export function ConversationView() {
   const myAvatarFileId = meQuery.data?.profile.avatar_file_id;
   const peerAvatarFileId = isSelf ? myAvatarFileId : peerProfileQuery.data?.avatar_file_id;
   const headerAvatarFileId = isGroup ? groupProfileQuery.data?.avatar_file_id : peerAvatarFileId;
+  // Color-hash id, not the file lookup above -- topicId is right for a group (its own identity), but
+  // for P2P this should be the peer's stable usr id (peerUserId), matching the same hash ContactsListColumn/
+  // FriendProfileView use for this same person, rather than the p2p topic name (which isP2P/self also
+  // never had a usr-shaped id for in the first place).
+  const headerAvatarId = isGroup ? topicId : peerUserId || topicId;
   // `peerName` is the GROUP's own name for a group topic, not any member's -- reusing it to label
   // "who is being quoted" (as both the reply-composer preview and the actual sent quote block used
   // to) meant every single group-chat reply permanently displayed "回复 <群名>：…" for every member,
@@ -824,7 +837,7 @@ export function ConversationView() {
                 <Icon name="arrow_back_ios_new" />
               </Link>
               <button type="button" onClick={onToggleDetail} className="flex items-center gap-2.5 text-left">
-                <Avatar id={topicId} name={peerName} avatarFileId={headerAvatarFileId} className="h-9.5 w-9.5 flex-none rounded-lg text-sm" />
+                <Avatar id={headerAvatarId} name={peerName} avatarFileId={headerAvatarFileId} className="h-9.5 w-9.5 flex-none rounded-lg text-sm" />
                 <div className="flex flex-col">
                   <strong className="text-base font-semibold text-text-heading">
                     {peerName}