Add .NET 11 / EF Core 11 support; remove .NET 8 +semver: major

[erenken]

This release removes .NET 8 / EF Core 8 support and adds .NET 11 / EF Core 11 RC2 support. The library, SQLite sample, and tests now target .NET 10 and .NET 11. Applications still targeting .NET 8 must remain on the earlier 0.x package line.

Breaking change and versioning

• Set GitVersion's next-version: 1.0.0 so the next main release advances from 0.x to 1.0.0, including after a squash merge without a version directive. The commit and PR title also carry +semver: major.
• Call out the .NET 8 removal and migration requirements in both READMEs, the changelog, and NuGet release notes.
• Verify the 0.x-to-1.0.0 squash-merge scenario, tagged reruns, and the subsequent 1.0.1 patch. Remove the version hint after v1.0.0 is tagged.

Framework and packaging changes

• Use SDK 11.0.100-rc.2.26504.105 and EF Core / dependency injection 11.0.0-rc.2.26504.105 for the new target; retain .NET 10 / EF Core 10.
• Update CI SDK installation and require exactly the two supported framework assets, symbols, and matching EF Core dependency groups in package validation.
• Suppress only packaging warning NU5104 for the intentional EF Core 11 RC2 dependency. Remove this exception when adopting EF Core 11 GA.
• Preserve the dependency and GitHub Actions updates already merged into main.

Validation

• Release build: zero warnings or errors.
• SQLite test suite: 29 passed on .NET 10 and 29 passed on .NET 11 (58 total), with coverage collected.
• NuGet and symbol packages build; packaged DLL/PDB identities, versions, dependency groups, and Source Link downloads/checksums pass for both frameworks.
• GitVersion regression scenarios, workflow lint, and whitespace checks pass.