Remove the unused box-sizing.scss stylesheet and its import from the main SCSS index file.
Update all Vue component template class references from the custom border-box class to the
native box-border utility class to eliminate redundant custom CSS and align with the project's
utility class conventions.
Remove the unused padding.scss stylesheet and its import from the main SCSS entrypoint. Update all legacy padding utility class names across every Vue component to use inline pixel-based utility classes (such as replacing `pl-12` with `pl-[12px]`). Also clean up extraneous whitespace and line breaks in component templates for improved readability.
Replace all custom `bg-*` utility classes across Vue components with Tailwind's arbitrary hex color notation (e.g. `bg-[#f7f7f7]`). Remove redundant hardcoded background color definitions from src/static/scss/background.scss, clean up template formatting, and update gradient button styles to use direct hex values.
