feat: extract Python adapters and initialize models asynchronously

[paulirish]

Description

• Extracts PyAnnote, Parakeet, and Canary logic into dedicated Python scripts within `internal/transcription/adapters/py/`.
• Updates `Makefile` and `ci.yaml` to run `pytest` on these extractions.
• Introduces `cmd/setup-adapters` for environment initialization.
• Refactors model adapter registration to happen centrally in `registry.go` and runs them asynchronously during server startup.

[paulirish]

apologies i didnt intend to make these PRs!