修复禅道Bug清单中的前端问题：好友申请source校验、群解散二次验证缺失、

群解散事件未处理、错误码翻译缺失、恢复登录页误导性提示

- 好友申请首次必失败30000（P0）：AddFriendModal把手机号搜索单独标记为
  source:"phone"上报，但后端serveIMFriendRequestCreate的source校验只认
  search/qr/group，命中default分支返回"invalid friend request source"。
  改为手机号搜索也统一上报source:"search"（后端本就不区分具体搜索渠道），
  用两个全新、此前无任何关系的测试账号验证首次申请200成功
- 解散群聊需要短信二次验证但完整流程从未实现（P0）：新增
  SecurityChallengeModal通用二次验证弹层（POST /security/challenges→
  验证码→verify→action_token）+ requestActionToken()（stores/
  securityChallenge.ts，与requestConfirm同一模式），接入解散群聊和转让
  群主（后者此前也因缺X-Action-Token必然404/400）。同时发现并修复
  imDelete对无body请求不显式传空对象体，导致携带Content-Type:
  application/json但请求体真正为空时后端JSON解码失败返回400——实测确认
  两个问题都解决后DELETE返回200
- 群聊被解散但当前正查看该群的用户界面不会跳转（P1）：新增
  topics.ts的subscribeTopicGone()监听SDK自身的onDeleteTopic回调，
  ConversationView据此在当前会话被解散时弹出提示并跳转回消息列表
- P2P会话发起方标题栏显示原始topic id、对方明明在线却显示离线：确认
  为上一轮已修复的isCommType()根因问题的同一症状，本轮实测（新建从未
  聊过天的账号对）已不再复现；群内消息发送者显示原始uid的关联描述同样
  实测未复现
- 好友关系冲突（已是好友/申请正在处理中）报错英文原文透出：翻译表补充
  FRIEND_REQUEST_CONFLICT
- 深链/刷新页面时的"改为重新登录"链接此前在任何恢复登录过程中都会
  立即显示（不管是否超时），造成短暂白屏时的误导性提示：改为仅在真正
  超时后才显示该链接，与其上方的提示文案保持一致的显示条件

web/src/lib/api/groups.ts

@@ -130,9 +130,17 @@ export function leaveGroup(topic: string) {
   return imPost<{ topic: string; status: string }>(`/groups/${encodeURIComponent(topic)}/leave`, {});
 }
 
-/** doc-flagged 待实现 (not yet implemented server-side) -- kept typed and ready for when it lands. */
-export function disbandGroup(topic: string) {
-  return imDelete<{ topic: string; deleted: boolean }>(`/groups/${encodeURIComponent(topic)}`);
+/** Needs `X-Action-Token` (two-factor-guarded write, docs/IM-前后端对接文档.md §6.17) -- get one via
+ *  `requestActionToken({scene:'group_dissolve', ...})` (stores/securityChallenge.ts) first. Live,
+ *  fully implemented server-side (a stale comment here previously claimed otherwise) -- confirmed by
+ *  actually calling it. An explicit empty-object body is required: a bodiless DELETE still carries
+ *  this client's own `Content-Type: application/json` header, and the server's JSON decoder treats
+ *  a truly empty body under that header as malformed rather than "no optional fields provided". */
+export function disbandGroup(topic: string, actionToken: string) {
+  return imDelete<{ topic: string; deleted: boolean }>(`/groups/${encodeURIComponent(topic)}`, {
+    body: {},
+    headers: { 'X-Action-Token': actionToken },
+  });
 }
 
 export type GroupRole = 'owner' | 'admin' | 'member';
@@ -264,14 +272,14 @@ export function unmuteGroupMember(topic: string, userId: string) {
   return imDelete<{ user_id: string; muted: boolean }>(`/groups/${encodeURIComponent(topic)}/mutes/${encodeURIComponent(userId)}`);
 }
 
-/** Needs `X-Action-Token` (two-factor-guarded write, docs/IM-前后端对接文档.md §6.26) -- not yet
- *  wired since no risk-challenge flow is built anywhere in this app yet; calling this will 409 until
- *  that's added. Kept typed so the group-management UI can be built ahead of that. */
-export function transferGroupOwner(topic: string, targetUserId: string, version: number) {
-  return imPost<{ owner: string; previous_owner: string; version: number }>(`/groups/${encodeURIComponent(topic)}/owner-transfer`, {
-    target_user_id: targetUserId,
-    version,
-  });
+/** Needs `X-Action-Token` (two-factor-guarded write, docs/IM-前后端对接文档.md §6.26) -- get one via
+ *  `requestActionToken({scene:'group_owner_transfer', ...})` (stores/securityChallenge.ts) first. */
+export function transferGroupOwner(topic: string, targetUserId: string, version: number, actionToken: string) {
+  return imPost<{ owner: string; previous_owner: string; version: number }>(
+    `/groups/${encodeURIComponent(topic)}/owner-transfer`,
+    { target_user_id: targetUserId, version },
+    { headers: { 'X-Action-Token': actionToken } },
+  );
 }
 
 export function getGroupGovernance(topic: string) {