Feature: don't cap bevy framerate when out of focus

[nondescriptpointer]

Bevy's default behavior limits the framerate when the window is out of focus. Does not seem relevant for our use case, especially during debugging and profiling.

Summary by CodeRabbit

• New Features

  • Automatically enables flatscreen mode when a desktop display environment is detected.
  • Ensures continuous updates in flatscreen mode even when the app window is unfocused, improving smoothness.
  • Improves input handling for flatscreen mode for a more responsive desktop experience.

• Refactor

  • Centralizes flatscreen mode detection behind a single environment-aware flag to streamline initialization and plugin setup.