fix(app): screenshot copy button copies image; add copy link

app-frontend/src/pages/ScreenshotsPage.vue

@@ -98,13 +98,25 @@ async function copyLink(item) {
 
 async function copyImage(item) {
   const url = buildUrl(item.filename)
+  if (
+    !navigator.clipboard ||
+    typeof navigator.clipboard.write !== 'function' ||
+    typeof window.ClipboardItem === 'undefined'
+  ) {
+    ElMessage.warning('当前环境不支持复制图片（建议使用 Chrome/Edge 并通过 HTTPS 访问）；可用“复制链接/下载”。')
+    return
+  }
+
   try {
     const resp = await fetch(url, { credentials: 'include' })
+    if (!resp.ok) throw new Error('fetch_failed')
     const blob = await resp.blob()
+    const mime = blob.type || ''
+    if (!mime.startsWith('image/')) throw new Error('not_image')
     await navigator.clipboard.write([new ClipboardItem({ [blob.type]: blob })])
     ElMessage.success('图片已复制')
   } catch {
-    await copyLink(item)
+    ElMessage.warning('复制图片失败：请确认允许剪贴板权限；可用“复制链接/下载”。')
   }
 }
 
@@ -142,6 +154,7 @@ onMounted(load)
             <div class="shot-meta app-muted">{{ item.created || '' }}</div>
             <div class="shot-actions">
               <el-button size="small" text type="primary" @click="copyImage(item)">复制图片</el-button>
+              <el-button size="small" text @click="copyLink(item)">复制链接</el-button>
               <el-button size="small" text @click="download(item)">下载</el-button>
               <el-button size="small" text type="danger" @click="onDelete(item)">删除</el-button>
             </div>