fix(date-picker): add the color for the container

[alejandrocabriales]

Ticket

• https://trello.com/c/99yfWLjD/1323-set-default-background-as-white-for-the-datepicker-component-in-document-engineering

Description

This update adjusts the component’s styling by applying adding theme-aware background colors (bg-white for light mode and dark:bg-slate-600 for dark mode).

PR Author Checklist:

• I have performed a self-review of my own code
• I have performed a self-review of my own chromatic changes and everything is expected
• I have removed any unnecessary console messages and alerts
• I have removed any commented code
• I have checked that there are no dummy or unnecessary comments
• I have added new test cases (if it applies)
• I have not introduced any linting issues or warnings

Screenshots (if apply)