design/visibility: make current date more visible

Is your feature request related to a problem? Please describe.

hi, so I'm always opening the calendar in the month view. And I'm using the dark mode of nextcloud. So it looks all kinda the same. the last and next month I can tell apart because of the lighter gray. But I am always searching for the current date for like a minute. Contributing to the problem is the fact that the personal calendar is kept in a similar color by default.

Describe the solution you'd like

I would like the date to be highlighted more. Maybe make a colored frame around the date? or change the current date color to some bright neon?

Describe alternatives you've considered

I changed the personal calendar to a different color, but the current date just doesn't stand out visually from the rest of the month.

Additional context

No response

No file or test is named. Start by locating the calendar month-view styling and the current-date state, then review how dark mode and calendar colors affect its contrast. Done means the current date is consistently more visible in the month view without reducing readability elsewhere.