Implemented Discord OAuth2 authentication flow with a new Discord.cs handler and integrated it into Program.cs. Refactored authentication logic to use shared JsonSerializerOptions from LauncherConstants. Updated BashUtils with cross-platform URL opening, improved MojangAPI to use shared HttpClient, and enhanced frontend login and log handling in logged.js and login.js.
Introduces MojangAPI utility for handling skin uploads, cape management, and username changes via new backend endpoints. Updates Program.cs to support new IPC commands for skin selection, uploading, cape toggling, and username changes. Refactors frontend (logged.js, logged.html, logged.css) to provide UI for skin uploads, cape selection, and username changes, including new styles and blank cape asset. Refactors UserRecord to allow username mutation.
