Add watcher routes to backend and frontend; implement routing and UI components for watcher management

frontend/src/App.vue

@@ -78,6 +78,7 @@ const pageTitle = computed(() => {
     'settings-password': 'Passwort ändern',
     'settings-timewish': 'Zeitwünsche',
     'settings-invite': 'Einladen',
+    'settings-permissions': 'Berechtigungen',
     'entries': 'Einträge',
     'stats': 'Statistiken'
   }