fix: 修复代理卡密统计和列表查询逻辑

- 前端使用后端返回的total字段显示总数
- 后端查询条件兼容旧数据(agent_id IS NULL AND creator_id = ?)
- handleGetStats统计接口使用相同查询逻辑

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/pages/agent/cards/index.vue

@@ -15,6 +15,7 @@ const router = useRouter()
 
 const loading = ref(true)
 const cards = ref<Card[]>([])
+const total = ref(0)
 const tableRef = ref()
 const searchFilter = ref('')
 
@@ -42,17 +43,22 @@ async function fetchCards() {
     const data = await api.get<any>('/agent/cards')
     if (Array.isArray(data)) {
       cards.value = data
+      total.value = data.length
     } else if (data?.cards) {
       cards.value = data.cards
+      total.value = data.total || data.cards.length
     } else if (data?.data) {
       cards.value = Array.isArray(data.data) ? data.data : []
+      total.value = data.total || cards.value.length
     } else {
       cards.value = []
+      total.value = 0
     }
   }
   catch (error) {
     console.error('Load cards failed:', error)
     cards.value = []
+    total.value = 0
   }
   finally {
     loading.value = false
@@ -111,7 +117,7 @@ onMounted(() => {
           </UiCardHeader>
           <UiCardContent>
             <div class="text-2xl font-bold">
-              {{ cards.length }}
+              {{ total }}
             </div>
           </UiCardContent>
         </UiCard>