Add Mod Loader, OptiFine Installation, and Modpack Import Support

I suggest improving the official Minecraft Launcher with these features: 1: Mod loader installation: Add one-click installation for compatible Fabric, Forge, NeoForge, and Quilt versions. 2: OptiFine installation: Support one-click installation of compatible versions and explain compatibility limits. 3: Mod management: Let players view, install, remove, enable, disable, and update mods, with dependency and conflict warnings. 4: Separate profiles: Keep each profile’s mods, configs, and game files isolated so vanilla, modded versions, and modpacks cannot interfere. 5: Modpack import: Support MCBBS v2 ZIPs (mcbbs.packmeta), Modrinth .mrpack files (modrinth.index.json), CurseForge ZIP exports (manifest.json and overrides), and compatible MultiMC/Prism instance archives (mmc-pack.json or instance.cfg). Detect formats by metadata, not file extension alone. 6: Automated installation: Preview pack details, install the required Minecraft version and loader, fetch dependencies, apply configs and overrides, verify files, show progress, and create a separate profile without overwriting existing ones. Explain missing files and incompatibilities clearly. 7: Modpack discovery: Allow browsing and installation of supported modpacks, respecting creators’ licenses and distribution rules. 8: Mainland China downloads: Improve speed and reliability through authorized regional infrastructure or mirrors, resumable downloads, and file integrity checks.