[no-need-to-merge] After geocoding, self-host pmtiles

[hexylena]

I really like our new map theme which focuses on public transit, https://www.öpnvkarte.de/
I found it on the 'free tileservers' list and I believe we are safe to use it.

Absolutely. The map is available under the conditions of the CC-BY-SA and ODbL licences (also for commercial use). That means you have to give information about the data source at a suitable place. This can be done for example by an attribution like "Map memomaps.de CC-BY-SA, map data Openstreetmap ODbL".

But in case we ever can't, here's our backup. Based on https://til.simonwillison.net/gis/pmtiles, this'll add an extracted .pmtiles to the event, next to the event, with the relevant map data. They're about 2.7 MB each which is heavy but, also aproximately the size of galaxy's libs.js (and they still need 'analysis' at 2.8, and 'app' at 2.1 MB) so, I think we're fine.

i'll setup the PR in a separate action anyway (for the geocoding, #4961)

todo:

• download the ./pmtiles binary from the latest releases