What changed

• Add radio memories as a SpotModel-backed feed for the panadapter
• Add a Memories toggle in SpotHub display settings and the legacy spot settings dialog
• Make memory spot clicks apply the selected memory instead of following the normal DX spot trigger path
• Keep memory spots in sync when memories are added, edited, or removed from the memory dialog

Why

• This lets saved memories be visualized on the panadapter and clicked to tune around quickly
• It keeps the feature Qt-native and cross-platform without changing existing DX spot behavior
• This PR resolves issue Add Memory spots in SpotHub #568

Validation

• cmake -S . -B build
• cmake --build build -j4
• cmake -S . -B build-cpu-spectrum -DAETHER_GPU_SPECTRUM=OFF
• cmake --build build-cpu-spectrum -j4