Implement batch user retrieval in AdminController and update routes

- Added a new method `getUsers` in AdminController to handle batch retrieval of user information based on hashed IDs.
- Updated adminRouter to include a new route for batch user retrieval.
- Enhanced AdminService with a method to fetch user details by hashed IDs, ensuring proper access control.
- Updated localization files to include the new "username" field for user connections in both German and English.
- Modified ServicesStatusView to utilize the new batch user retrieval for displaying usernames alongside connection counts.

backend/routers/adminRouter.js

@@ -18,6 +18,7 @@ router.delete('/chat/rooms/:id', authenticate, adminController.deleteRoom);
 // --- Users Admin ---
 router.get('/users/search', authenticate, adminController.searchUsers);
 router.get('/users/statistics', authenticate, adminController.getUserStatistics);
+router.get('/users/batch', authenticate, adminController.getUsers);
 router.get('/users/:id', authenticate, adminController.getUser);
 router.put('/users/:id', authenticate, adminController.updateUser);