Replace MultichannelAudioSource with CaptureAudioSource, add
ProcessedAudioSource (audio_source_id + audio_processing_template_id),
remove MonoAudioSource and BandExtractAudioSource entirely.
Update store resolution to walk processed chains collecting template IDs.
Update all API schemas, routes, and frontend references.
Add the foundation for audio processing filters, mirroring the existing
picture filter/postprocessing template system:
- AudioFilter base class, AudioFilterRegistry, AudioFilterOptionDef
- AudioProcessingTemplate dataclass + SQLite-backed store
- audio_filter_template meta-filter with recursive resolution
- Full REST API: CRUD templates + filter registry discovery
- Dependency injection wired in dependencies.py and main.py
alexei.dolgolyov