Adds background asset scanning and loading to improve editor responsiveness.
Updates the file browser with grid and list views, filtering, and callbacks for file selection.
Fixes an issue where the asset manager would block the main thread during asset loading.
Removes Assimp dependency.
Changes the asset loading process to use a queue system for texture uploads to OpenGL, which improves performance by offloading the texture loading to the main thread.
The asset manager now directly loads texture data using stb_image and uploads it to the GPU in the main thread, eliminating the need for Assimp.
