[ HumanjavaEnterprises/nostr-dm-magiclink-utils ] fix: update tests for key validation error messages and magicLink removal

Update nip04 test to expect new key validation error message.
Rewrite magiclink service tests to extract tokens from mock DM calls
instead of result.magicLink (removed for security in previous commit).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
https://github.com/HumanjavaEnterprises/nostr-dm-magiclink-utils/commit/7d96b32ead432fb47d1bf596fabdd2e6aa23dcba