feat(auth): reclaim stale identities and refresh profile UI

frontend/src/components/layout/AppHeader.vue

@@ -74,10 +74,14 @@
             class="flex items-center gap-2 rounded-xl p-1.5 transition-colors hover:bg-gray-100 dark:hover:bg-dark-800"
             aria-label="User Menu"
           >
-            <div
-              class="flex h-8 w-8 items-center justify-center rounded-xl bg-gradient-to-br from-primary-500 to-primary-600 text-sm font-medium text-white shadow-sm"
-            >
-              {{ userInitials }}
+            <div class="flex h-8 w-8 items-center justify-center overflow-hidden rounded-xl bg-gradient-to-br from-primary-500 to-primary-600 text-sm font-medium text-white shadow-sm">
+              <img
+                v-if="avatarUrl"
+                :src="avatarUrl"
+                :alt="displayName"
+                class="h-full w-full object-cover"
+              >
+              <span v-else>{{ userInitials }}</span>
             </div>
             <div class="hidden text-left md:block">
               <div class="text-sm font-medium text-gray-900 dark:text-white">
@@ -232,6 +236,7 @@ const dropdownOpen = ref(false)
 const dropdownRef = ref<HTMLElement | null>(null)
 const contactInfo = computed(() => appStore.contactInfo)
 const docUrl = computed(() => appStore.docUrl)
+const avatarUrl = computed(() => user.value?.avatar_url?.trim() || '')
 
 // 只在标准模式的管理员下显示新手引导按钮
 const showOnboardingButton = computed(() => {