fix(projects): disable cancel button during file upload and remove duplicate button

- Add `disabled={uploading}` prop to cancel button to prevent interaction during upload
- Remove duplicate button group that was causing redundant UI elements
- Ensure consistent button state management during file upload operations

frontend/src/pages/Projects.tsx

@@ -665,7 +665,7 @@ export default function Projects() {
                   </div>
 
                   <div className="flex justify-end space-x-4 pt-4 border-t-2 border-dashed border-gray-200 mt-auto">
-                    <Button variant="outline" onClick={() => setShowCreateDialog(false)} className="terminal-btn-primary bg-white text-black hover:bg-gray-100">
+                    <Button variant="outline" onClick={() => setShowCreateDialog(false)} disabled={uploading} className="terminal-btn-primary bg-white text-black hover:bg-gray-100">
                       取消
                     </Button>
                     <Button
@@ -676,12 +676,6 @@ export default function Projects() {
                       {uploading ? '上传中...' : '执行创建'}
                     </Button>
                   </div>
-
-                  <div className="flex justify-end space-x-4 pt-4 border-t-2 border-dashed border-gray-200">
-                    <Button variant="outline" onClick={() => setShowCreateDialog(false)} disabled={uploading} className="terminal-btn-primary bg-white text-black hover:bg-gray-100">
-                      取消
-                    </Button>
-                  </div>
                 </TabsContent>
               </Tabs>
             </div>