Fix badge download cap at 256 preventing large achievement sets from fully downloading

[clintonium-119]

Summary

• Fixes badge images not downloading for games with large achievement sets (e.g. Pokemon Unbound being the largest with 844 achievements)
• MAX_CACHED_BADGES was hardcoded to 256, but both locked and unlocked badge variants are cached per achievement, so any game with more than 128 achievements would silently drop badges
• Increased limit from 256 to 2048 (supports up to 1,024 achievements), at a cost of ~184 KB of static memory on AArch64
• Removed the redundant MAX_QUEUED_DOWNLOADS constant — the download queue and badge cache are structurally coupled and must always be the same size, so both now use MAX_CACHED_BADGES