Fix #347: Fix NameError in open_file timeout message (#351)

- Fix undefined 'timeout' variable in error message
- Use defined TIMEOUT constant instead of undefined timeout variable
- Prevents NameError when LibreOffice crashes during file opening

desktop_env/server/main.py

@@ -1370,7 +1370,7 @@ def open_file():
         if window_found:
             return "File opened and window activated successfully"
         else:
-            return f"Failed to find window for {file_name} within {timeout} seconds.", 500
+            return f"Failed to find window for {file_name} within {TIMEOUT} seconds.", 500
 
     except Exception as e:
         return f"Failed to open {path}. Error: {e}", 500