feat: initial commit of p3x-gitlist project}
- Add PHP backend with Silex-based framework and Gitter git library - Add Twig templates for repository browsing, commits, blame, tree, and network views - Add browser-side JavaScript with CodeMirror, syntax highlighting, and markdown support - Add SCSS styles with 25+ Bootswatch theme variants and dark/light mode switching - Add multi-language support with 29 translation files - Add Grunt build system and Webpack configuration for frontend assets - Add Docker support with Dockerfile, docker-compose.yml, and init scripts - Add Nginx configuration and Apache .htaccess for web server deployment - Add Composer dependencies and Yarn/npm package configuration - Add GitHub Actions CI workflow for automated builds - Add PHPUnit test suite for Gitter client, repository, and commit models - Add project documentation including README, INSTALL guide, and changelog - Add configuration examples for Linux and Windows environments - Add helper scripts for building, releasing, and optimizing git repositories