Enhance API key handling in settings and vocab services: Update key retrieval logic to improve validation and status reporting. Introduce new localization strings for key status messages in English, German, and Spanish. Update LanguageAssistantView to display key status dynamically, enhancing user feedback on API key management.

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

@@ -169,7 +169,10 @@
             "save": "Save",
             "saved": "Settings saved.",
             "saveError": "Could not save.",
-            "confirmClear": "Really delete the API key?"
+            "confirmClear": "Really delete the API key?",
+            "keyStatusStored": "API key stored.",
+            "keyStatusInvalid": "A stored API key exists, but it cannot be read. Please save it again.",
+            "keyStatusMissing": "No API key is currently stored."
         },
         "interests": {
             "title": "Interests",
@@ -198,4 +201,4 @@
             }
         }
     }
-}
+}