fix(frontend): 完善表单校验并添加错误提示

- UserEditModal: 添加 email 必填和 concurrency 最小值校验
- UserAttributesConfigModal: 添加 key/name 必填和 options 非空校验
- GroupsView: 添加 name 必填校验
- ProxiesView: 添加 name/host 必填和 port 范围校验
- UserBalanceModal: 添加 amount 有效性和余额充足性校验
- RedeemView: 添加空兑换码错误提示
- i18n: 添加所有新增校验的中英文翻译

frontend/src/views/admin/GroupsView.vue

@@ -871,6 +871,10 @@ const closeCreateModal = () => {
 }
 
 const handleCreateGroup = async () => {
+  if (!createForm.name.trim()) {
+    appStore.showError(t('admin.groups.nameRequired'))
+    return
+  }
   submitting.value = true
   try {
     await adminAPI.groups.create(createForm)
@@ -912,6 +916,10 @@ const closeEditModal = () => {
 
 const handleUpdateGroup = async () => {
   if (!editingGroup.value) return
+  if (!editForm.name.trim()) {
+    appStore.showError(t('admin.groups.nameRequired'))
+    return
+  }
 
   submitting.value = true
   try {

frontend/src/views/admin/ProxiesView.vue

@@ -887,6 +887,18 @@ const handleBatchCreate = async () => {
 }
 
 const handleCreateProxy = async () => {
+  if (!createForm.name.trim()) {
+    appStore.showError(t('admin.proxies.nameRequired'))
+    return
+  }
+  if (!createForm.host.trim()) {
+    appStore.showError(t('admin.proxies.hostRequired'))
+    return
+  }
+  if (createForm.port < 1 || createForm.port > 65535) {
+    appStore.showError(t('admin.proxies.portInvalid'))
+    return
+  }
   submitting.value = true
   try {
     await adminAPI.proxies.create({
@@ -927,6 +939,18 @@ const closeEditModal = () => {
 
 const handleUpdateProxy = async () => {
   if (!editingProxy.value) return
+  if (!editForm.name.trim()) {
+    appStore.showError(t('admin.proxies.nameRequired'))
+    return
+  }
+  if (!editForm.host.trim()) {
+    appStore.showError(t('admin.proxies.hostRequired'))
+    return
+  }
+  if (editForm.port < 1 || editForm.port > 65535) {
+    appStore.showError(t('admin.proxies.portInvalid'))
+    return
+  }
 
   submitting.value = true
   try {