- Rename `AuracastQosDefault` class to `AuracastQosRobust` to better reflect its characteristics (4 retransmissions)
- Replace RTN (retransmission number) dropdown with QoS preset selector offering "Fast" (2 RTN) and "Robust" (4 RTN) options
- Update frontend and backend to use QoS preset mapping instead of manual QoS config construction
- Add `_resolve_qos_preset_name()` helper function to convert QoS config