Add AWS Transcribe provider

[Kleenex-ultrasoft]

Summary

• add an --api aws Amazon Transcribe provider that uploads converted audio to S3 and starts/polls batch transcription jobs
• support optional transcript output bucket/prefix plus cleanup of uploaded media
• document AWS environment variables and add mocked unit coverage for job success, output-bucket retrieval, failure, config validation, and CLI routing

Validation

• .venv/bin/python -m unittest tests.test_aws -v
• .venv/bin/python -m compileall src tests
• .venv/bin/sapat --help
• git diff --check

No AWS credentials, audio files, or transcript artifacts are committed. This is the companion implementation for the Daytona content guide planned under daytonaio/content#13.

[Kleenex-ultrasoft]

Content guide PR for the Daytona bounty: daytonaio/content#247

Validation rerun after the Signed-off-by amend:

• .venv/bin/python -m unittest tests.test_aws -v -> 5 tests OK
• .venv/bin/python -m compileall src tests -> passed
• .venv/bin/sapat --help -> AWS provider appears in --api choices
• git diff --check -> passed

The current red Continue AI statuses report Agent encountered an error; I do not see a code/test failure from those checks.