UI - Replace Current Date Picker with HumHub Native Date Picker

Ideally, we use the native HumHub picker.

## Current Picker

<img width="1440" height="1024" alt="Image" src="https://github.com/user-attachments/assets/89664901-9308-4a7c-8bf1-73c662e6a09a" />

## HumHub Picker

<img width="1440" height="1024" alt="Image" src="https://github.com/user-attachments/assets/9c2dcaa6-825d-4d68-97e5-bd017380d72f" />