feat(styles): create global styles entry point and organize global styles
feat(styles): implement base HTML element styles and utility classes for flexbox
feat(styles): establish layout, position, spacing, and text utility classes
feat(styles): introduce mixins for animations, cards, dialogs, flexbox, grid, and responsive design
test(quick_guide): add component and metadata validation tests for quick_guide package
test(ui_level6): implement metadata validation tests for ui_level6 package
