feat(settings): add default subscriptions for new users

- add default subscriptions to admin settings

- auto-assign subscriptions on register and admin user creation

- add validation/tests and align settings UI with subscription selector patterns

frontend/src/views/admin/SettingsView.vue

@@ -579,7 +579,7 @@
               {{ t('admin.settings.defaults.description') }}
             </p>
           </div>
-          <div class="p-6">
+          <div class="space-y-6 p-6">
             <div class="grid grid-cols-1 gap-6 md:grid-cols-2">
               <div>
                 <label class="mb-2 block text-sm font-medium text-gray-700 dark:text-gray-300">
@@ -613,6 +613,98 @@
                 </p>
               </div>
             </div>
+
+            <div class="border-t border-gray-100 pt-4 dark:border-dark-700">
+              <div class="mb-3 flex items-center justify-between">
+                <div>
+                  <label class="font-medium text-gray-900 dark:text-white">
+                    {{ t('admin.settings.defaults.defaultSubscriptions') }}
+                  </label>
+                  <p class="text-sm text-gray-500 dark:text-gray-400">
+                    {{ t('admin.settings.defaults.defaultSubscriptionsHint') }}
+                  </p>
+                </div>
+                <button
+                  type="button"
+                  class="btn btn-secondary btn-sm"
+                  @click="addDefaultSubscription"
+                  :disabled="subscriptionGroups.length === 0"
+                >
+                  {{ t('admin.settings.defaults.addDefaultSubscription') }}
+                </button>
+              </div>
+
+              <div
+                v-if="form.default_subscriptions.length === 0"
+                class="rounded border border-dashed border-gray-300 px-4 py-3 text-sm text-gray-500 dark:border-dark-600 dark:text-gray-400"
+              >
+                {{ t('admin.settings.defaults.defaultSubscriptionsEmpty') }}
+              </div>
+
+              <div v-else class="space-y-3">
+                <div
+                  v-for="(item, index) in form.default_subscriptions"
+                  :key="`default-sub-${index}`"
+                  class="grid grid-cols-1 gap-3 rounded border border-gray-200 p-3 md:grid-cols-[1fr_160px_auto] dark:border-dark-600"
+                >
+                  <div>
+                    <label class="mb-1 block text-xs font-medium text-gray-600 dark:text-gray-400">
+                      {{ t('admin.settings.defaults.subscriptionGroup') }}
+                    </label>
+                    <Select
+                      v-model="item.group_id"
+                      class="default-sub-group-select"
+                      :options="defaultSubscriptionGroupOptions"
+                      :placeholder="t('admin.settings.defaults.subscriptionGroup')"
+                    >
+                      <template #selected="{ option }">
+                        <GroupBadge
+                          v-if="option"
+                          :name="(option as unknown as DefaultSubscriptionGroupOption).label"
+                          :platform="(option as unknown as DefaultSubscriptionGroupOption).platform"
+                          :subscription-type="(option as unknown as DefaultSubscriptionGroupOption).subscriptionType"
+                          :rate-multiplier="(option as unknown as DefaultSubscriptionGroupOption).rate"
+                        />
+                        <span v-else class="text-gray-400">
+                          {{ t('admin.settings.defaults.subscriptionGroup') }}
+                        </span>
+                      </template>
+                      <template #option="{ option, selected }">
+                        <GroupOptionItem
+                          :name="(option as unknown as DefaultSubscriptionGroupOption).label"
+                          :platform="(option as unknown as DefaultSubscriptionGroupOption).platform"
+                          :subscription-type="(option as unknown as DefaultSubscriptionGroupOption).subscriptionType"
+                          :rate-multiplier="(option as unknown as DefaultSubscriptionGroupOption).rate"
+                          :description="(option as unknown as DefaultSubscriptionGroupOption).description"
+                          :selected="selected"
+                        />
+                      </template>
+                    </Select>
+                  </div>
+                  <div>
+                    <label class="mb-1 block text-xs font-medium text-gray-600 dark:text-gray-400">
+                      {{ t('admin.settings.defaults.subscriptionValidityDays') }}
+                    </label>
+                    <input
+                      v-model.number="item.validity_days"
+                      type="number"
+                      min="1"
+                      max="36500"
+                      class="input h-[42px]"
+                    />
+                  </div>
+                  <div class="flex items-end">
+                    <button
+                      type="button"
+                      class="btn btn-secondary default-sub-delete-btn w-full text-red-600 hover:text-red-700 dark:text-red-400"
+                      @click="removeDefaultSubscription(index)"
+                    >
+                      {{ t('common.delete') }}
+                    </button>
+                  </div>
+                </div>
+              </div>
+            </div>
           </div>
         </div>
 
@@ -1157,9 +1249,17 @@
 import { ref, reactive, computed, onMounted } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { adminAPI } from '@/api'
-import type { SystemSettings, UpdateSettingsRequest } from '@/api/admin/settings'
+import type {
+  SystemSettings,
+  UpdateSettingsRequest,
+  DefaultSubscriptionSetting
+} from '@/api/admin/settings'
+import type { AdminGroup } from '@/types'
 import AppLayout from '@/components/layout/AppLayout.vue'
 import Icon from '@/components/icons/Icon.vue'
+import Select from '@/components/common/Select.vue'
+import GroupBadge from '@/components/common/GroupBadge.vue'
+import GroupOptionItem from '@/components/common/GroupOptionItem.vue'
 import Toggle from '@/components/common/Toggle.vue'
 import { useClipboard } from '@/composables/useClipboard'
 import { useAppStore } from '@/stores'
@@ -1181,6 +1281,7 @@ const adminApiKeyExists = ref(false)
 const adminApiKeyMasked = ref('')
 const adminApiKeyOperating = ref(false)
 const newAdminApiKey = ref('')
+const subscriptionGroups = ref<AdminGroup[]>([])
 
 // Stream Timeout 状态
 const streamTimeoutLoading = ref(true)
@@ -1193,6 +1294,16 @@ const streamTimeoutForm = reactive({
   threshold_window_minutes: 10
 })
 
+interface DefaultSubscriptionGroupOption {
+  value: number
+  label: string
+  description: string | null
+  platform: AdminGroup['platform']
+  subscriptionType: AdminGroup['subscription_type']
+  rate: number
+  [key: string]: unknown
+}
+
 type SettingsForm = SystemSettings & {
   smtp_password: string
   turnstile_secret_key: string
@@ -1209,6 +1320,7 @@ const form = reactive<SettingsForm>({
   totp_encryption_key_configured: false,
   default_balance: 0,
   default_concurrency: 1,
+  default_subscriptions: [],
   site_name: 'Sub2API',
   site_logo: '',
   site_subtitle: 'Subscription to API Conversion Platform',
@@ -1257,6 +1369,17 @@ const form = reactive<SettingsForm>({
   min_claude_code_version: ''
 })
 
+const defaultSubscriptionGroupOptions = computed<DefaultSubscriptionGroupOption[]>(() =>
+  subscriptionGroups.value.map((group) => ({
+    value: group.id,
+    label: group.name,
+    description: group.description,
+    platform: group.platform,
+    subscriptionType: group.subscription_type,
+    rate: group.rate_multiplier
+  }))
+)
+
 // LinuxDo OAuth redirect URL suggestion
 const linuxdoRedirectUrlSuggestion = computed(() => {
   if (typeof window === 'undefined') return ''
@@ -1316,6 +1439,14 @@ async function loadSettings() {
   try {
     const settings = await adminAPI.settings.getSettings()
     Object.assign(form, settings)
+    form.default_subscriptions = Array.isArray(settings.default_subscriptions)
+      ? settings.default_subscriptions
+          .filter((item) => item.group_id > 0 && item.validity_days > 0)
+          .map((item) => ({
+            group_id: item.group_id,
+            validity_days: item.validity_days
+          }))
+      : []
     form.smtp_password = ''
     form.turnstile_secret_key = ''
     form.linuxdo_connect_client_secret = ''
@@ -1328,9 +1459,60 @@ async function loadSettings() {
   }
 }
 
+async function loadSubscriptionGroups() {
+  try {
+    const groups = await adminAPI.groups.getAll()
+    subscriptionGroups.value = groups.filter(
+      (group) => group.subscription_type === 'subscription' && group.status === 'active'
+    )
+  } catch (error) {
+    console.error('Failed to load subscription groups:', error)
+    subscriptionGroups.value = []
+  }
+}
+
+function addDefaultSubscription() {
+  if (subscriptionGroups.value.length === 0) return
+  const existing = new Set(form.default_subscriptions.map((item) => item.group_id))
+  const candidate = subscriptionGroups.value.find((group) => !existing.has(group.id))
+  if (!candidate) return
+  form.default_subscriptions.push({
+    group_id: candidate.id,
+    validity_days: 30
+  })
+}
+
+function removeDefaultSubscription(index: number) {
+  form.default_subscriptions.splice(index, 1)
+}
+
 async function saveSettings() {
   saving.value = true
   try {
+    const normalizedDefaultSubscriptions = form.default_subscriptions
+      .filter((item) => item.group_id > 0 && item.validity_days > 0)
+      .map((item: DefaultSubscriptionSetting) => ({
+        group_id: item.group_id,
+        validity_days: Math.min(36500, Math.max(1, Math.floor(item.validity_days)))
+      }))
+
+    const seenGroupIDs = new Set<number>()
+    const duplicateDefaultSubscription = normalizedDefaultSubscriptions.find((item) => {
+      if (seenGroupIDs.has(item.group_id)) {
+        return true
+      }
+      seenGroupIDs.add(item.group_id)
+      return false
+    })
+    if (duplicateDefaultSubscription) {
+      appStore.showError(
+        t('admin.settings.defaults.defaultSubscriptionsDuplicate', {
+          groupId: duplicateDefaultSubscription.group_id
+        })
+      )
+      return
+    }
+
     const payload: UpdateSettingsRequest = {
       registration_enabled: form.registration_enabled,
       email_verify_enabled: form.email_verify_enabled,
@@ -1340,6 +1522,7 @@ async function saveSettings() {
       totp_enabled: form.totp_enabled,
       default_balance: form.default_balance,
       default_concurrency: form.default_concurrency,
+      default_subscriptions: normalizedDefaultSubscriptions,
       site_name: form.site_name,
       site_logo: form.site_logo,
       site_subtitle: form.site_subtitle,
@@ -1538,7 +1721,18 @@ async function saveStreamTimeoutSettings() {
 
 onMounted(() => {
   loadSettings()
+  loadSubscriptionGroups()
   loadAdminApiKey()
   loadStreamTimeoutSettings()
 })
 </script>
+
+<style scoped>
+.default-sub-group-select :deep(.select-trigger) {
+  @apply h-[42px];
+}
+
+.default-sub-delete-btn {
+  @apply h-[42px];
+}
+</style>