ShareBox: self-hosted file sharing with video streaming in pure PHP

ShareBox is a self-hosted file sharing platform built in pure PHP 8.1 with zero runtime dependencies — no Laravel, no Symfony, just SQLite and native stdlib. It handles adaptive video streaming with on-the-fly FFmpeg remuxing or transcoding, human-readable slugs, and explicit security handling for CSRF, session fixation, and directory traversal. A practical deep-dive for developers who want full control over what they ship.