Modernize dependencies and split ASP.NET integration

[MikeChristensen]

Summary

• target .NET 8 and .NET 10 and update the supported dependency stack
• replace Core and DB log4net usage with Microsoft.Extensions.Logging
• move AddKPCContext into the new KitchenPC.Core.AspNetCore package
• upgrade FluentNHibernate, NHibernate, Npgsql, and the test stack
• add NuGet vulnerability enforcement, Dependabot, and three-package CI/release publishing
• update tests, README guidance, and the Core wiki for the 2.0 migration

Package impact

This prepares three matching 2.0 packages:

• KitchenPC.Core
• KitchenPC.DB
• KitchenPC.Core.AspNetCore

The middleware namespace remains KitchenPC.Core.Middleware, so web consumers add the new package without changing their using directive.

Verification

• Release solution build: succeeded with 0 warnings and 0 errors for net8.0 and net10.0
• Core unit tests on net10.0: 39 passed
• Samples tests against local DLLs: 20 passed
• Website tests against local DLLs: 16 passed
• PostgreSQL smoke test: recipe list/detail and shopping-list NLP aggregation succeeded against KPCSample
• generated and inspected all three local NuGet packages; project dependency versions match
• NuGet vulnerability audit: no vulnerable direct or transitive packages

The net8.0 test assemblies build successfully. They were not executed locally because this workstation currently has only the .NET 10 runtime; CI installs both runtimes and will execute the multi-target suite.