fix(mail): 邮箱选择改字符串绑定，修复切换后输入框显示未更新

src/views/mail/Mailbox.vue

@@ -75,6 +75,15 @@ const changePwdForm = ref({ OldPassword: '', NewPassword: '', ConfirmPassword: '
 const myAddress = computed(() => selectedMailbox.value?.MailboxName || '')
 const mailboxCount = computed(() => myMailboxes.value.length)
 const atMailboxLimit = computed(() => myMailboxes.value.length >= 5)
+/** 登录页邮箱选择：字符串驱动显示，避免 el-select 对象引用匹配失效 */
+const selectedName = computed({
+  get: () => selectedMailbox.value?.MailboxName || '',
+  set: (name: string) => {
+    const hit = myMailboxes.value.find((m) => m.MailboxName === name)
+    if (hit) selectedMailbox.value = hit
+    loginForm.value.Password = ''
+  },
+})
 
 // === 本地已读覆盖 ===
 // Stalwart v0.11 存在 JMAP keywords 写入已知 bug（GitHub #1139）：setSeen 返回成功但已读随机回退未读，
@@ -726,14 +735,14 @@ function isSelected(id: string): boolean {
             </div>
             <el-select
               v-if="myMailboxes.length > 1"
-              v-model="selectedMailbox"
+              v-model="selectedName"
               class="login-address-select"
               placeholder="选择要登录的邮箱"
             >
               <el-option
                 v-for="m in myMailboxes"
                 :key="m.MailboxName"
-                :value="m"
+                :value="m.MailboxName"
                 :label="m.MailboxName"
                 :disabled="m.Status !== 1"
               />