- Share links are now short: the share button makes `/share/<code>` links
  that open on any copy of the app, follow the aircraft, military aircraft or
  satellite you were following, and fall back to its last-known position with
  a notice if it isn't reporting. A mistyped link is refused instead of
  opening a different view. Long `#v=2` links keep working (samehkhamis, #1418).