Add in-app local API key setup

Let fresh Docker and local installs enter OpenSky, AIS, and other provider keys directly in onboarding or Settings without manually creating .env files. Persist keys server-side in the backend data store, keep them write-only from the browser, reload runtime settings, and retain local-operator access controls.

backend/services/config.py

@@ -302,6 +302,11 @@ class Settings(BaseSettings):
 
 @lru_cache
 def get_settings() -> Settings:
+    try:
+        from services.api_settings import load_persisted_api_keys_into_environ
+        load_persisted_api_keys_into_environ()
+    except Exception:
+        pass
     return Settings()