Show all Meshtastic devices - add old data to the map

[daskalovst]

The map is displaying Meshtastic devices that are currently inactive. These devices are listed in the nodeDB but haven't been seen for several days, yet they still show up on the map. I think need to be adjusted it so that only active devices are shown. After 900 seconds of inactivity (assuming the default parameter for position updates), the inactive devices should turn black and disappear from the map. or at least to have some indicator that shows when the device are seen for last time

In the remarks section, there is a timestamp, but it's in a format like "1713103054," which isn't readable for humans at all.

It seems that nodeDB isn't a reliable source for this information because it's not functioning correctly. but that's different topic...