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/components/admin/user/UserBalanceModal.vue

@@ -37,10 +37,21 @@ watch(() => props.show, (v) => { if(v) { form.amount = 0; form.notes = '' } })
 
 const calculateNewBalance = () => (props.user ? (props.operation === 'add' ? props.user.balance + form.amount : props.user.balance - form.amount) : 0)
 const handleBalanceSubmit = async () => {
-  if (!props.user) return; submitting.value = true
+  if (!props.user) return
+  if (!form.amount || form.amount <= 0) {
+    appStore.showError(t('admin.users.amountRequired'))
+    return
+  }
+  if (props.operation === 'subtract' && form.amount > props.user.balance) {
+    appStore.showError(t('admin.users.insufficientBalance'))
+    return
+  }
+  submitting.value = true
   try {
     await adminAPI.users.updateBalance(props.user.id, form.amount, props.operation, form.notes)
     appStore.showSuccess(t('common.success')); emit('success'); emit('close')
-  } catch {} finally { submitting.value = false }
+  } catch (e: any) {
+    appStore.showError(e.response?.data?.detail || t('common.error'))
+  } finally { submitting.value = false }
 }
 </script>

frontend/src/components/admin/user/UserEditModal.vue

@@ -86,6 +86,14 @@ const copyPassword = async () => {
 }
 const handleUpdateUser = async () => {
   if (!props.user) return
+  if (!form.email.trim()) {
+    appStore.showError(t('admin.users.emailRequired'))
+    return
+  }
+  if (form.concurrency < 1) {
+    appStore.showError(t('admin.users.concurrencyMin'))
+    return
+  }
   submitting.value = true
   try {
     const data: any = { email: form.email, username: form.username, notes: form.notes, concurrency: form.concurrency }

frontend/src/components/user/UserAttributesConfigModal.vue

@@ -344,6 +344,18 @@ const removeOption = (index: number) => {
 }
 
 const handleSave = async () => {
+  if (!form.key.trim()) {
+    appStore.showError(t('admin.users.attributes.keyRequired'))
+    return
+  }
+  if (!form.name.trim()) {
+    appStore.showError(t('admin.users.attributes.nameRequired'))
+    return
+  }
+  if ((form.type === 'select' || form.type === 'multi_select') && form.options.length === 0) {
+    appStore.showError(t('admin.users.attributes.optionsRequired'))
+    return
+  }
   saving.value = true
   try {
     const data = {