Release StreamDeck-Tools v7.0.0 with migration guide

- Bump version from 7.0.0-beta.4 to 7.0.0

- Add MigrateTo7.0.md: comprehensive migration guide with type mapping, method tables, code recipes, tiers, deprecation timeline

- Update README.md with v7.0 release notes and migration guide link

- Update NUGET.md with modern quick-start and v7.0 features

- Restore barraider-sdtools/README.md with v7.0 changelog entry

- Update SamplePlugin to net10.0 with SkiaSharp-only KeyPressed

- Fix csproj README path reference (../README.md)

Made-with: Cursor

Author: BarRaider