Fix recorder finalize path and add invite-gated login

.env.example

@@ -3,6 +3,7 @@ PORT=3000
 # App auth / storage / database
 DATABASE_URL=mysql://tennis:replace-with-db-password@db:3306/tennis_training_hub
 JWT_SECRET=replace-with-strong-secret
+REGISTRATION_INVITE_CODE=CA2026
 VITE_APP_ID=tennis-training-hub
 OAUTH_SERVER_URL=
 OWNER_OPEN_ID=