Mirrors the desktop spec changes for the new shared transcript
pipeline. These config/dep files are NOT auto-synced (they have
desktop-only divergences elsewhere) so this is a manual mirror.
- config/default_config.py: new transcript.upload_audio_only field
(default true). Set to false to fall back to uploading the
source video instead of the extracted mp3.
- config/config_loader.py: settings.yml is chmod 0o600'd on POSIX
after every save() so the now-plaintext transcript.api_key isn't
world-readable. chmod failures only WARN; save() still succeeds.
- pyproject.toml + requirements.txt: pin imageio-ffmpeg==0.6.0 as
a runtime dep (first version with native macOS arm64 wheel).
Bumps requires-python to 3.9 to match imageio-ffmpeg 0.6's lower
bound.
