修复文章编辑表单无法提交的问题

- 移除嵌套的附件上传form（HTML不允许表单嵌套）
- 改用div和JavaScript FormData处理附件上传

app/templates/admin/article_form.html

@@ -387,6 +387,39 @@ editor.addEventListener('input', updatePreview);
 
 // 初始化预览
 updatePreview();
+
+// 附件上传函数
+{% if article %}
+function uploadAttachment() {
+    const formData = new FormData();
+    formData.append('article_id', document.getElementById('attachment-article-id').value);
+    formData.append('file', document.getElementById('attachment-upload-file').files[0]);
+    formData.append('description', document.getElementById('attachment-desc').value);
+    
+    fetch('{{ url_for("admin.upload_attachment") }}', {
+        method: 'POST',
+        body: formData
+    })
+    .then(res => res.json())
+    .then(data => {
+        if (data.success) {
+            location.reload();
+        }
+    });
+}
+
+function deleteAttachment(id) {
+    if (confirm('确定删除此附件？')) {
+        fetch(`/admin/attachment/${id}/delete`, {method: 'POST'})
+        .then(res => res.json())
+        .then(data => {
+            if (data.success) {
+                location.reload();
+            }
+        });
+    }
+}
+{% endif %}
 </script>
 {% endblock %}
 
@@ -515,43 +548,13 @@ updatePreview();
             </div>
             {% endfor %}
         </div>
-        <form id="attachment-upload-form" enctype="multipart/form-data">
-            <input type="hidden" name="article_id" value="{{ article.id }}">
-            <input type="file" name="file" id="attachment-upload">
-            <input type="text" name="description" placeholder="文件描述（可选）" style="display: inline-block; width: 200px;">
+        <div class="attachment-upload-area">
+            <input type="hidden" id="attachment-article-id" value="{{ article.id }}">
+            <input type="file" id="attachment-upload-file">
+            <input type="text" id="attachment-desc" placeholder="文件描述（可选）" style="display: inline-block; width: 200px;">
             <button type="button" onclick="uploadAttachment()" class="btn btn-sm btn-secondary">上传附件</button>
-        </form>
+        </div>
     </div>
-    
-    <script>
-    function uploadAttachment() {
-        const form = document.getElementById('attachment-upload-form');
-        const formData = new FormData(form);
-        
-        fetch('{{ url_for("admin.upload_attachment") }}', {
-            method: 'POST',
-            body: formData
-        })
-        .then(res => res.json())
-        .then(data => {
-            if (data.success) {
-                location.reload();
-            }
-        });
-    }
-    
-    function deleteAttachment(id) {
-        if (confirm('确定删除此附件？')) {
-            fetch(`/admin/attachment/${id}/delete`, {method: 'POST'})
-            .then(res => res.json())
-            .then(data => {
-                if (data.success) {
-                    location.reload();
-                }
-            });
-        }
-    }
-    </script>
     {% endif %}
     
     <div class="form-group">