fix: 明确提示超大 PNG 像素限制

app/pages/admin/media.vue

@@ -90,7 +90,7 @@ const formatBytes = (bytes: number) => bytes < 1024 * 1024 ? `${Math.ceil(bytes
       <div v-if="loading" class="admin-loading">正在加载素材…</div>
       <div v-else class="media-admin-body">
         <section v-if="view === 'active'" class="media-upload-panel editor-panel">
-          <div><PhUploadSimple :size="30" /><strong>上传新图片</strong><small>支持 JPG、PNG、WebP；最大 8MB、4000 万像素</small></div>
+          <div><PhUploadSimple :size="30" /><strong>上传新图片</strong><small>支持 JPG、PNG、WebP；最大 8MB、4000 万像素。Logo 建议使用透明 PNG，宽度 600–1600px</small></div>
           <div class="media-upload-meta"><input v-model="uploadMeta.altText" placeholder="ALT 描述（建议填写）"><input v-model="uploadMeta.source" placeholder="素材来源"><input v-model="uploadMeta.copyright" placeholder="版权/授权说明"><select v-model="uploadMeta.authorizationStatus"><option value="pending">待核验</option><option value="authorized">已授权</option><option value="restricted">限制使用</option></select></div>
           <label class="media-upload-button"><input type="file" accept="image/jpeg,image/png,image/webp" :disabled="busy" @change="upload">{{ busy ? '处理中…' : '选择并上传图片' }}</label>
         </section>