Implement birthdate input in member profile management. Update API to handle birthdate data for user profiles and enhance visibility settings for birthday display in member lists.

server/api/profile.get.js

@@ -26,6 +26,7 @@ export default defineEventHandler(async (event) => {
         name: user.name,
         email: user.email,
         phone: user.phone || '',
+        geburtsdatum: user.geburtsdatum || '',
   visibility: Object.assign({ showBirthday: true }, (user.visibility || {}))
       }
     }