fix: prevent migration rollback failure when NULL values exist

priv/repo/migrations/20260102155350_remove_phone_number_and_make_fields_optional.exs

@@ -203,6 +203,11 @@ defmodule Mv.Repo.Migrations.RemovePhoneNumberAndMakeFieldsOptional do
   end
 
   def down do
+    # Set default values for NULL fields before restoring NOT NULL constraint
+    # This prevents the migration from failing if NULL values exist
+    execute("UPDATE members SET first_name = '' WHERE first_name IS NULL")
+    execute("UPDATE members SET last_name = '' WHERE last_name IS NULL")
+
     # Restore first_name and last_name as NOT NULL
     execute("ALTER TABLE members ALTER COLUMN first_name SET NOT NULL")
     execute("ALTER TABLE members ALTER COLUMN last_name SET NOT NULL")