Normalize all Python sources to the standard ADN copyright block with
complete GPLv3 notice. Add legacy attribution on routing and dmr_utils
ports; drop SemVer wording from changelog and fix an unused test import.
- Use DefaultVoiceProvider when Audio dir exists (was gated by ANNOUNCEMENT_LANGUAGES)
- Create Audio dir at startup when voice config present
- ANNOUNCEMENT_LANGUAGES optional (ident only); each item has own LANGUAGE
- ident: fallback to per-system ANNOUNCEMENT_LANGUAGE when empty
- disconnected_voice: use system language directly
- Clarify ENABLED, ANNOUNCEMENT_LANGUAGES in adn-voice.example.yaml
- Add Audio/.gitkeep, update .gitignore to keep folder structure