Traffic Signs date filters

[ireun]

Hello there!

First of all Thank You for maintaining this plugin! <3

Now I'd like to share my feedback (and maybe some tips for other users)

1. Did what you suggested in Add Filter for Mapillary Traffic Sign layer #227 - I probably wouldn't have found the mapillary-traffic-signs-source layer myself
2. I converted this layer to OSM data to poke around
3. This layer, on it's own seems to have no icons in it?
4. After adding normal Mapillary Traffic Signs layer and disabling it the Icons are now visible.
5. Indeed these points have epoch timestamps in them
6. So I can do a normal JOSM filter with something like last_seen_at > 1672531200000 and it shows me all signs found in 2023! Great!
7. Unfortunately "Mapillary Filter" date dialog sets a wrong filter!
   
   It doesn't use the timestamp but a date! This filter shows nothing.
8. Again manually setting the filter to last_seen_at > 1672531200000 works.
   

So I think point no. 7 should be fixed?