bug: `/v1/files/` invalid filename will hang the server

[gau-nernst]

Cortex version

dev 2e1dfa0

Describe the issue and expected behaviour

Something like this will hang the server

curl http://127.0.0.1:3928/v1/files -X POST -F "data=@libvulkan.so;filename=../hi" -F purpose=assistants

Digging further, I find that this loop never exits in such cases https://github.com/menloresearch/cortex.cpp/blob/2e1dfa02ccdf7816b02223f01d95e658c7296fa8/engine/repositories/file_fs_repository.cc#L20-L25

We might want to just sanitize the filename as a string instead of a path i.e. no weird characters, including /. This will also solve an issue if the filename appears to be a subdirectory

curl http://127.0.0.1:3928/v1/files -X POST -F "data=@libvulkan.so;filename=abc/hello" -F purpose=assistants
{"message":"Failed to open file for writing: <redacted>/cortexcpp/files/abc/hello"}

(or we can just store the binary file in a DB 😆)

Steps to Reproduce

No response

Screenshots / Logs

No response

What is your OS?

• Windows
• Mac Silicon
• Mac Intel
• Linux / Ubuntu

What engine are you running?

• cortex.llamacpp (default)
• cortex.tensorrt-llm (Nvidia GPUs)
• cortex.onnx (NPUs, DirectML)

Hardware Specs eg OS version, GPU

No response