Stale audio files loop while user thinks it's live

[dthaler]

Describe the bug
Sunset Bay is currently offline, with an old latest.txt file.
live.orcasound.net has a play button for Sunset Bay that plays the last audio stored, and loops.
The user has no way to know it's not live, however, and might report "new" (actually old) detections, and might even do so multiple times as it loops.

To Reproduce
go to live.orcasound.net
go to Sunset Bay
click play

Expected behavior
User should be informed that it isn't live.
For example it could show the node as down.