Add Microsoft Store MSIX packaging

[StephanOrgiazzi]

Summary

• add a Microsoft Store MSIX manifest using the reserved Partner Center identity for PLAY.
• package PLAY. as a full-trust desktop app with the existing video file associations
• generate Store logo assets from the existing PLAY. icon during packaging
• stage the Tauri executable, bundled libmpv runtime/licenses, and shaders into the MSIX
• map PLAY. semantic versions to Store-compatible four-part package versions (0.16.0 -> 1.16.0.0)
• verify the generated MSIX by unpacking it and checking required runtime files
• add a Windows GitHub Actions workflow that builds and uploads the unsigned Store package
• document the Store release path and expose bun run release:store

Partner Center identity:

• Identity Name: DevJamStudio.622382E8743A9
• Publisher: CN=300C6CAC-B727-40B2-8FF0-4C00EBAF31D9
• Publisher Display Name: Dev Jam Studio
• Store ID: 9NXXT91JCTHX

The package is intentionally unsigned. Microsoft Store signs MSIX packages after certification.