Emby5 v1.2.1

This is a small update focused on improving the startup experience.

Previously, Emby5 would sit on a black screen while initializing everything in the background. I've reworked the startup process so the new branded splash screen appears much earlier, with a progress bar showing the loading stages before taking you to the main interface.

What's changed

• Added a new Emby5 splash screen.
• Reduced the black screen during startup.
• Reworked the initialization order so the splash appears before the rest of the app loads.
• Added a progress bar that follows the actual startup process rather than a fixed timer.