Phrasync v0.4.3

This source release brings GitHub up to date with Phrasync 0.4.3. Since the first release: a native Windows window, English/Italian UI, visible model-download progress, NVIDIA GPU support where available, longer subtitle projects, richer 3D scenes including Lost in the Ocean, better lyric timing, and improved MP4 export with a chosen destination and Japanese font fallback. Version 0.4.3 also fixes stale interface assets after an in-place Store update and adds in-app Store update checks and a diagnostics panel. The Microsoft Store build is still in certification; no installer is attached to this GitHub release. Existing Store users should back up important projects, uninstall an earlier version once, then install 0.4.3 from the Store when available. See RELEASE_NOTES.md for details and the remaining update-flow verification limit.