Encrypt traffic to keep the network private

Add encryption so we can avoid showing outsiders' messages and devices in the dashboard. It's mostly people transmitting from airplanes that we're picking up. I think they aren't supposed to do that.

No files, tests, or entry points are identified in the issue. Start by tracing how the EVALink service receives transmissions and exposes devices or messages in the dashboard, then determine the required encryption scope and trust model. Done should include a documented way to verify that unauthorized traffic and device data are not exposed.

Written by the indexing model from the issue text.