Add /upload_sample route to allow upload new speakers using Web API

[abeiro]

• Added route to upload sample into speakers folder, so you can upload new speakers using API
• Added python-multipart to requirements

Summary by CodeRabbit

• New Features

  • Introduced a new endpoint for uploading WAV files, which saves the file and returns the filename.
  • Added a Jupyter Notebook for a comprehensive setup guide to deploy the AI text-to-speech server using the X-TTS API.

• Dependencies

  • Added python-multipart package to support file uploads.