refactor(m0): restructure project and install dependencies

- Clean Avalonia template content (ViewLocator, greeting, empty Models folder)
- Add YKanBan.Tests (MSTest 4.4.1) to solution
- Install packages per plan version table (Semi.Avalonia, Lucide icons,
  Microsoft.Data.Sqlite, Pidgin, Newtonsoft.Json 13.0.4 fallback)

YKanBan.slnx

@@ -1,3 +1,4 @@
 <Solution>
   <Project Path="YKanBan/YKanBan.csproj" />
+  <Project Path="YKanBan.Tests/YKanBan.Tests.csproj" />
 </Solution>