fix(ui): move warm-up to startup

[saadndm]

Warm-up

• Moved from world loading screen to the MC startup loading screen so that OC can be opened in titlescreen smoothly
• Removed background class preloading (required classes already loaded in warmup, and didnt work anyways because it targeted wrong modid)
• Removes search focus warmup (benchmark shows it has no stutter and previous one didnt work anyways)
• Holds startup loading screen until warm-up finishes (15s timeout)

Ui State and cleanup

• Fixes sometimes opening the Mods page scrolled to the bottom by resetting scroll position after warm-up
• Clears navigation history after warm-up
• Centralized error logging and cleanup in ComposePreloader.failStartup()

Font loading

• Registered skia font listener before MC's initial resource reload, and moved it to a worker so that it doesn't use the synchronous fallback

Icons

• Fixes icon preload cache keys not matching paths, and made it actually reuse cached file bytes