Update the release pipeline for both packages

[chrispader]

Summary

• Add a dedicated GitHub Actions release workflow for manual versioned releases
• Update release automation to publish both react-native-nitro-sqlite and react-native-nitro-sqlite-vec
• Keep package versions and example dependency pins aligned during release
• Add release metadata and prepublish checks to the vec package

Testing

• Not run (not requested)
• Validated the release flow changes by inspecting the updated workflow, package release-it config, and shell release script for both package publish paths