群昵称改用专门的接口读取，修好读不回已保存值的问题

上一个commit修好了"群资料"页把群名称当成个人群昵称显示的问题，但实机验证发现改完仍然显示"未设置"。
抓包确认根因：GET /groups/{topic}/members 列表接口的每一项里压根没有 group_nickname 字段（只有
acs/display_name/mentionable/role/user_id），所以任何从成员列表里读昵称的写法，不管代码逻辑对不对，
都永远拿不到值——这个文件里原有的 MyNicknameEditor 也是同样的写法，同样存在这个问题（打开编辑器时
不会回填已保存的昵称）。

真正能读到昵称的是保存用的那个路径上对应的 GET：GET /groups/{topic}/members/me/profile，返回
{nickname, version, updated_at}（server/im_http.go:4776-4782）。im-api.js 里之前只封装了 PUT，
补上了对应的 getMyGroupProfile，两处读取（群资料页预览行、昵称编辑器回填）都改成用它。

实机验证：保存"测试昵称A"后重新打开群资料页，"群昵称"正确显示"测试昵称A"，"群名称"独立显示
"扫码测试群"。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/views/group-management-view.jsx

@@ -5,7 +5,7 @@ import { pinyin } from 'pinyin-pro';
 import HashNavigation from '../lib/navigation.js';
 import {
   getGroups, createGroup, getGroup, updateGroup, getGroupSettings, updateGroupMemberSettings,
-  updateMyGroupProfile, leaveGroup, getGroupMembers, createGroupQRCode, getGroupJoinRequests,
+  updateMyGroupProfile, getMyGroupProfile, leaveGroup, getGroupMembers, createGroupQRCode, getGroupJoinRequests,
   acceptGroupJoinRequest, rejectGroupJoinRequest, getLatestGroupAnnouncement,
   updateCurrentGroupAnnouncement, getGroupGovernance, updateGroupGovernance, addGroupAdmins,
   deleteGroupAdmin, muteGroupMembers, getGroupMutes, unmuteGroupMember, transferGroupOwner,
@@ -400,8 +400,10 @@ function GroupProfile({topic, myUserId, onToast}) {
   const [loadError, setLoadError] = React.useState(false);
   // "群昵称" here means "my nickname within this group" (see MyNicknameEditor below), not the group's
   // own name -- confirmed live this preview row was showing group.name instead, since it's easy to
-  // conflate the two. Reuses the same getGroupMembers+filter approach MyNicknameEditor already uses
-  // (there's no working "me" shortcut on the member-profile-by-id endpoint to fetch this more directly).
+  // conflate the two. GET .../members/me/profile is the only endpoint that actually returns this --
+  // confirmed live that the member list endpoint (getGroupMembers) never includes group_nickname on
+  // any item, so a version of this fix that read it from there (like MyNicknameEditor below does)
+  // would always show "未设置" even right after a successful save.
   const [myNickname, setMyNickname] = React.useState('');
   React.useEffect(() => {
     if (!topic) return;
@@ -409,12 +411,11 @@ function GroupProfile({topic, myUserId, onToast}) {
     getGroup(topic).then(g => { writeCachedData('group:' + topic, g); setGroup(g); }).catch(() => { onToast('加载失败'); setLoadError(true); });
   }, [topic]);
   React.useEffect(() => {
-    if (!topic || !myUserId) return;
-    getGroupMembers(topic, {query: ''}).then(data => {
-      const me = (data.items || []).find(m => m.user_id === myUserId);
-      if (me) setMyNickname(me.group_nickname || '');
+    if (!topic) return;
+    getMyGroupProfile(topic).then(data => {
+      setMyNickname(data.nickname || '');
     }).catch(() => {});
-  }, [topic, myUserId]);
+  }, [topic]);
   if (!group) return <div className="group-page"><Header title="群资料" back="group-settings" backTopic={topic} /><main className="group-profile"><p className="group-inline-empty">{loadError ? '群组信息加载失败' : '加载中…'}</p></main></div>;
   const canEdit = group.permissions && group.permissions.can_edit_profile;
   const nicknameLabel = myNickname || '未设置';
@@ -865,15 +866,14 @@ function GroupDescriptionEditor({topic, onToast}) {
 // "我在本群的昵称" has no dedicated reference screenshot (see plan notes) -- placed in GroupSettings,
 // governed by the real member_invite... no, by the group_nickname field on groupMemberPayload, gated by
 // the "群成员修改昵称" concept the images described (server-side enforcement, not re-checked client-side).
-function MyNicknameEditor({topic, myUserId, onToast}) {
+function MyNicknameEditor({topic, onToast}) {
   const [value, setValue] = React.useState('');
+  // getGroupMembers' list items never include group_nickname (confirmed live) -- only
+  // GET .../members/me/profile actually returns it, same fix as GroupProfile's preview row above.
   React.useEffect(() => {
-    if (!topic || !myUserId) return;
-    getGroupMembers(topic, {query: ''}).then(data => {
-      const me = (data.items || []).find(m => m.user_id === myUserId);
-      if (me) setValue(me.group_nickname || '');
-    }).catch(() => {});
-  }, [topic, myUserId]);
+    if (!topic) return;
+    getMyGroupProfile(topic).then(data => setValue(data.nickname || '')).catch(() => {});
+  }, [topic]);
   const save = () => {
     updateMyGroupProfile(topic, value.trim(), 0).then(() => {
       onToast('保存成功'); window.setTimeout(() => navigate('group-settings', topic), 600);