Update nostr gem, switch to Ruby for bech32 encoding

spec/models/user_spec.rb

@@ -205,4 +205,14 @@ RSpec.describe User, type: :model do
       end
     end
   end
+
+  describe "#nostr_pubkey_bech32" do
+    before do
+      user.update! nostr_pubkey: "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"
+    end
+
+    it "encodes the hexadecimal pubkey to bech32" do
+      expect(user.nostr_pubkey_bech32).to eq("npub1qlsc3g0lsl8pw8230w8d9wm6xxcax3f6pkemz5measrmwfxjxteslf2hac")
+    end
+  end
 end