Update nostr gem, switch to Ruby for bech32 encoding

app/models/user.rb

@@ -1,3 +1,5 @@
+require 'nostr'
+
 class User < ApplicationRecord
   include EmailValidatable
 
@@ -185,6 +187,11 @@ class User < ApplicationRecord
     ldap.delete_attribute(dn,:service)
   end
 
+  def nostr_pubkey_bech32
+    return nil unless nostr_pubkey.present?
+    Nostr::PublicKey.new(nostr_pubkey).to_bech32
+  end
+
   private
 
     def ldap