Refactor Nostr settings/connect

* Use NIP-42 auth event instead of short text note
* Verify event ID and signature using the nostr gem instead of custom code

app/controllers/application_controller.rb

@@ -63,4 +63,9 @@ class ApplicationController < ActionController::Base
     @fetch_balance_retried = true
     lndhub_fetch_balance
   end
+
+  def nostr_event_from_params
+    params.permit!
+    params[:signed_event].to_h.symbolize_keys
+  end
 end