KingdomMod v0.2.8 - Same-version MSI upgrade fix

What's changed

• Allows same-version MSI upgrades so rebuilt installers replace the existing KingdomMod entry instead of creating a duplicate Appwiz entry.
• Fixes the duplicate KingdomMod 0.2.7 scenario caused by testing/installing multiple MSI builds with the same version but different ProductCodes.
• Keeps downgrade protection in place for genuinely newer installed versions.

Validation

• Installed 0.2.8 over local 0.2.7 and confirmed Appwiz had one KingdomMod entry.
• Rebuilt 0.2.8, installed it over the existing 0.2.8, and confirmed Appwiz still had one KingdomMod entry.