feat: update audio merging service

[drewcook]

General Changes

• Adds in utilities for working with ffmpeg
  • Adds in utility for merging multiple audio blobs together to a singular one
  • Adds in utility to fetch a file and/or use it for transcoding, mainly just stubs this out but doesn't use it
• Applies new merge utility to minting/buying projects as nfts and cuts down time spent sending to python service
• Removes all references to python merge backend service, completely decoupling the UI from it

Developer Notes

Add any notes here that may be helpful for reviewers.

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Author Checklist

• The base branch is set to main
• The title is using Conventional Commit formatting
• The Github issue has been linked to the PR in the Development section
• The General Changes section has been filled out
• Developer Notes have been added (optional)

Reviewer Checklist

• End-to-end tests are passing without any errors
• Code style generally follows existing patterns
• New third-party packages, if any, do not introduce potential security threats
• There are no CI changes, or they have been OK’d by the devops team
• Code changes have been quality checked in the ephemeral URL
• There is at least one approval from the core team
• Squash and merge has been checked

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