- Introduce `Streamtype` enum (Continuous vs Finite) to distinguish radio streams from finite tracks
- Enrich `TrackBoundary` sync marker with stream type for proper pause behavior per mode (silence vs backpressure)
- Update all sources and sinks to pass `StreamType` when creating track boundaries
- Radio Paradise, HTTP source → Continuous (infinite)
- Improve UPnP control architecture: pause sends silence for radio, blocks pipeline via backpressure for tracks
- Prepare groundwork for multi-client DSP architecture with shared source and per-DSP pipelines
