Stability hotfix

This is a hotfix for a rare but significant bug:

• Fixed memory leaks which could lead to major graphical glitches. After playing for some amount of time, UI and game elements would disappear or start showing garbage. (The amount of time was dependent on in-game activity and framerate; faster computers experienced this sooner.)

And a few other bugfixes:

• Fixed: Tutorial skips two screens when pressing Space/Enter.

• Fixed: Unlocked tutorials don't appear in list until level change.

To ensure stability and improve future bug reporting, I took the opportunity to make a few other tweaks, without any gameplay changes:

• Windows-only: switched graphics API from Vulkan to Direct3D 12. This should have no noticeable effect, but was strongly recommended by the Godot team due to various video driver bugs in Vulkan. In the event of a graphics issue, you can switch back by going to game Properties in Steam, and adding "--[c]rendering-driver vulkan[/c]" to Launch Options, but I don't anticipate this will be needed.

• The "Version Info" screen in Settings now displays which graphics API is being used, the video card model and driver versions.

• The game now logs its own version number on startup (to the log files in [c]%AppData%\\Celestial Golf\\logs[/c] which can be helpful in diagnosing problems).

• Updated Godot engine version from 4.7 to 4.7.1 (this should have no noticeable effect).

Thanks to everyone who reported and helped diagnose these issues!