Add notification on relay-search for explaining still wrong first_seen date in corner cases

We had issues with our ´first_seenb` date for relays (see: onionoo#40042 (closed)). It would be smart to show some notification on relay-search as we still have corner cases (e.g. for relays older than 5 years) where the bug is unfixed.

We could think about a general notification bar but it would be neat if we only showed the notification for relays that are actually affected, if possible.