fix(file-manager): fix create-folder API to accept JSON request body

The create_folder endpoint was incorrectly defined to accept query
parameters instead of JSON request body, causing 400 errors when
called from the frontend.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

routes/file_manager.py

@@ -260,15 +260,20 @@ async def delete_item(path: str):
 
 
 @router.post("/create-folder")
-async def create_folder(path: str, name: str):
+async def create_folder(request: Dict[str, str]):
     """
     创建文件夹
 
     Args:
-        path: 父目录路径
-        name: 新文件夹名称
+        request: 包含path和name字段的JSON对象
     """
     try:
+        path = request.get("path", "")
+        name = request.get("name", "")
+
+        if not name:
+            raise HTTPException(status_code=400, detail="文件夹名称不能为空")
+
         parent_path = resolve_path(path) if path else resolve_path("projects")
         parent_path.mkdir(parents=True, exist_ok=True)