Migrate chapter 4 contracts solution to .NET 10 and add central package management

[meaboutsoftware]

📋 Description

This PR migrates the Fitnet.Contracts solution to .NET 10, introduces Central Package Management for better dependency consistency, and fixes the GitHub Actions workflow authentication to align with the main solution's configuration.

Key Changes:

• Migrated all Fitnet.Contracts projects from .NET 9 to .NET 10
• Implemented Central Package Management using Directory.Packages.props
• Updated workflow to use .NET 10.0.x (previously 9.0.x)
• Fixed workflow authentication by switching from add source to update source with local config file
• Corrected NUGET_SOURCE_NAME to EvolutionaryArchitecture for consistency
• Updated all NuGet packages to their latest .NET 10 compatible versions

Issue Resolved: Build pipeline was using .NET 9 and attempting to add a NuGet source that already existed in the local nuget.config, causing authentication failures.

📦 PR Includes

• Feature added 🆕 (Central Package Management)
• Bug fix 🐛 (GitHub Actions workflow authentication)
• Code refactor 🔄 (.NET 10 migration, package consolidation)
• Documentation update 📚
• Tests added/updated 🧪
• Other: Infrastructure upgrade to .NET 10

🚫 PR Does Not Include

• Breaking changes ❌
• Major architectural changes 🏗️
• Unrelated features/tasks 🚫

💡 Additional Notes

Central Package Management Benefits:

• Single source of truth for all package versions in Directory.Packages.props
• Eliminates version conflicts across Fitnet.Contracts projects
• Simplifies dependency updates and maintenance
• Aligns with .NET best practices and modern solution structure

Workflow Fix Details:

• Changed authentication approach from adding new source to updating existing source
• Added --configfile nuget.config to work with local configuration instead of global
• Fixed to use ${{ github.actor }} and ${{ secrets.GITHUB_TOKEN }}
• Corrected source name casing to EvolutionaryArchitecture (matching nuget.config)

Consistency Across Solutions:
All Chapter 4 solutions now follow the same patterns:

• ✅ Main Fitnet solution: .NET 10 + CPM ✓
• ✅ Fitnet.Common solution: .NET 10 + CPM ✓
• ✅ Fitnet.Contracts solution: .NET 10 + CPM ✓
• ✅ All workflows aligned and standardized