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.

frontend/src/i18n/locales/de/admin.json

@@ -256,6 +256,7 @@
                     "title": "Aktive Verbindungen",
                     "none": "Keine aktiven Verbindungen",
                     "userId": "Benutzer-ID",
+                    "username": "Benutzername",
                     "connections": "Verbindungen",
                     "duration": "Verbindungsdauer",
                     "lastPong": "Zeit seit letztem Pong",

frontend/src/i18n/locales/en/admin.json

@@ -256,6 +256,7 @@
                     "title": "Active Connections",
                     "none": "No active connections",
                     "userId": "User ID",
+                    "username": "Username",
                     "connections": "connections",
                     "duration": "Connection Duration",
                     "lastPong": "Time Since Last Pong",