Memory leak with zstd compression

[beavailable]

Downloading files and archives with zstd compression causes memory leaks on both linux and windows platforms.

How to reproduce:

1. Start the application:

   ./share.py

2. Use one of the following commands to download a file or an archive:

   curl --compressed -o /dev/null http://localhost:8888/any/file
   curl -o /dev/null http://localhost:8888/any/folder.tar.zst

3. Repeat step 2, you'll see it's memory usage increases.

Don't know why yet.

[beavailable]

With Python 3.14 and its built-in zstd compression, the memory leak seems to have disappeared.