fix: 修复非HTTPS环境下剪贴板复制失败问题

- 添加安全检查，仅在clipboard可用时尝试复制
- 添加错误处理，避免复制失败影响用户体验

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

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

@@ -108,11 +108,19 @@ async function handleGenerate() {
       card_type_id: Number(form.value.card_type_id),
       quantity: form.value.count,
     })
-    toast.success(t('agent.cards.create.generateSuccess', { count: data.codes.length }))
+    toast.success(t('agent.cards.create.generateSuccess', { count: data.codes?.length || 0 }))
 
-    const codesText = data.codes.join('\n')
-    await navigator.clipboard.writeText(codesText)
-    toast.success(t('agent.cards.create.copiedToClipboard'))
+    // 尝试复制到剪贴板（仅在安全上下文中可用）
+    if (data.codes?.length && navigator?.clipboard?.writeText) {
+      try {
+        const codesText = data.codes.join('\n')
+        await navigator.clipboard.writeText(codesText)
+        toast.success(t('agent.cards.create.copiedToClipboard'))
+      }
+      catch {
+        // 剪贴板复制失败，忽略
+      }
+    }
 
     router.push('/agent/cards')
   }