Updated the skin upload schema to accept both JSON and multipart/form-data content types, and to allow requests without a URL. Simplified the texture storage path in userService.js by removing subdirectory partitioning based on hash.
Introduces zod-based validation schemas for Minecraft and Mojang API endpoints. Refactors texture route to support hash-based file serving and removes the old static texture route. Updates database schema for player properties and adds an event to clean expired certificates. Improves ValidationError formatting, adjusts skin/cape URL construction, and adds SSRF protection for skin uploads.
