.NET: Update version for release

[Jacob Alber (lokitoth)]

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• [ ] Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[github-actions]

Automated Code Review

Reviewers: 4 | Confidence: 96% | Result: All clear

Reviewed: Correctness, Security Reliability, Test Coverage, Design Approach

---

Automated review by lokitoth's agents

[Copilot]

Pull request overview

Updates the .NET NuGet packaging metadata to align with the next release version (1.5.0), ensuring generated package versions and tags reflect the new release line.

Changes:

• Bumped the central NuGet VersionPrefix from 1.4.0 to 1.5.0.
• Updated DateSuffix to 260507 for preview/suffixed package version generation.
• Updated GitTag to 1.5.0 to match the new version prefix.