Port MacroRecorderGUI from WPF to WinUI 3 on modern .NET

Goal: replace the WPF UI with a C# WinUI 3 desktop UI on .NET 10 while preserving the existing recorder/playback behavior and native backend boundary. Scope: migrate UI, bindings, resources, commands, and lifecycle; keep RecordPlaybackDLL and protobuf behavior intact except minimal compatibility changes; support unpackaged desktop deployment without requiring the Store; remove superseded WPF code; update managed tests where practical. Acceptance: one coherent WinUI GUI covering current record/playback, hotkey, load/save, and macro-list interactions; native projects remain independently buildable; restore/build/tests run when tooling permits and exact environment blockers are documented; no unrelated behavior fixes.