Restructured `EnvelopeGenerator.DependencyInjection.csproj` to:
- Add multiple `PackageReference` entries for application services, ORM/Database, security/identity, utilities, and DI abstractions.
- Introduce conditional `ItemGroup` sections for `net7.0`, `net8.0`, and `net9.0` with framework-specific package versions.
- Move `UserManager` package reference to align with the updated dependency structure.
- Update comments for clarity, including replacing a Turkish comment with an English one.
- Add a comment explaining the rationale for centralizing `PackageReference` declarations to ensure correct `.nuspec` generation and simplify consumption.
TekH
823bafeeb9