feat(admin): align frontend with updated API contracts

src/views/auth/RegisterView.vue

@@ -2,6 +2,7 @@
 import { computed, ref } from 'vue'
 import { useRoute } from 'vue-router'
 import { NAlert, NButton, NCard, NForm, NFormItem, NInput, NResult } from 'naive-ui'
+import { ApiError } from '@/lib/api'
 import { useAuthStore } from '@/stores/auth'
 
 const authStore = useAuthStore()
@@ -15,13 +16,12 @@ const error = ref('')
 const loading = ref(false)
 const registered = ref(false)
 const emailDelivered = ref(true)
-
-const canResend = computed(() =>
-  error.value.includes('重发验证') || error.value.includes('已被注册，请使用重发'),
-)
+const registerConflict = ref(false)
+const canResend = computed(() => registerConflict.value)
 
 async function handleRegister() {
   error.value = ''
+  registerConflict.value = false
   const trimmedName = name.value.trim()
   const trimmedEmail = email.value.trim()
 
@@ -53,7 +53,12 @@ async function handleRegister() {
     emailDelivered.value = response.email_sent
     registered.value = true
   } catch (e: unknown) {
-    error.value = e instanceof Error ? e.message : '注册失败，请稍后重试'
+    if (e instanceof ApiError && e.status === 409) {
+      registerConflict.value = true
+      error.value = '邮箱或用户名已被占用；若邮箱尚未验证，可以尝试重发验证邮件。'
+    } else {
+      error.value = e instanceof Error ? e.message : '注册失败，请稍后重试'
+    }
   } finally {
     loading.value = false
   }