[SUBTASK]-Create Join Group Screen

[SturmDerLiebe]

Ressources

• Figma: https://www.figma.com/design/q5QkaCsXuGn3XACfOWjdHa?node-id=419-6283#1139687323

#Tasks

1. Create the Group Join Screen in app/group/join/page.tsx
2. Try to mimic the App Design to a reasonable extend, since on Desktop and MobileWeb some things feel better if combined on one screen.
   1. Orient yourself on the verification screen in app/authenticate/verify/page.tsx
   2. if not done yet, make the letter spacing width or em dependant
3. Use the GroupRepository join method