Make homepage default to a live hydrophone

[adrmac]

Issue description:
Currently, the live.orcasound.net home screen shows a player that is grayed out, because no specific hydrophone is selected.

Observed metrics:
Low rate of player starts per visit to the home screen, high bounce rate.

User story:
As a new user, I want to quickly understand what the app does after clicking "listen live" from the wordpress site or similar. When presented with a grayed out player, I may assume the app is not working.

User story:
As a concerned citizen scientist, I want to quickly tune in to my favorite hydrophone, or the one with the most recent confirmed detections.

Ideal solution:
Make the home screen default to the the hydrophone with the most recent confirmed detection.

Blockers:

• No automated way to mark detections as confirmed.
• No data import of confirmed detections from OrcaHello.

Interim solution:
For new users, make the home screen default to Orcasound Lab. For returning users, make the home screen default to their last selected hydrophone.

[scottveirs]

For reference, here's a screenshot of the current view on desktop when one browses to live.orcasound.net --

-- and here is the mobile view:

In both, one can see the grayed-out play button visible near the bottom of the UI.