Secure HTTP Skins

Fixes:

• Fixed Forge crash on launch: [1.20.1,1.20.1] version range replaced with [1.20.1,1.20.2)
• Removed broken TextureManagerMixin that caused mixin application failure

New:

• Config options in config/securehttpskins-common.toml:
• enableHttpsRedirect — toggle HTTP→HTTPS rewriting (default: true)
• enableSignatureBypass — toggle signature validation bypass for SkinRestorer (default: true)
• debugLogging — log every URL rewrite to console (default: false)
• excludedUrlPatterns — regex list of URLs to skip HTTPS rewrite
• F9 keybind — clears skin texture cache (rejoin world to re-download skins over HTTPS)
• Mod icon