✨(frontend) introduce a shortcut settings tab

Work adapted from PR #859 and partially extracted to ship as a
smaller, focused PR.

This allows users to view the full list of available shortcuts.
An editor to customize these shortcuts may be introduced later.

src/frontend/src/locales/de/settings.json

@@ -100,6 +100,11 @@
       }
     }
   },
+  "shortcuts": {
+    "listLabel": "Tastenkürzel",
+    "columnAction": "Aktion",
+    "columnShortcut": "Tastenkürzel"
+  },
   "dialog": {
     "heading": "Einstellungen"
   },
@@ -120,6 +125,7 @@
     "general": "Allgemein",
     "notifications": "Benachrichtigungen",
     "accessibility": "Barrierefreiheit",
-    "transcription": "Transkription"
+    "transcription": "Transkription",
+    "shortcuts": "Tastenkürzel"
   }
 }