fix(wildlife): point the Acartia card link only at acartia.io

The card's "Acartia" link was built from the contributor-supplied
photo_url, so any https site could appear labelled as Acartia. Acartia
has no documented per-sighting page, so the source link is now always
the Acartia site, on the server projection and again in the card.
The separate "Open on Acartia" fallback link is no longer needed.

src/i18n/locales/de.json

@@ -3153,7 +3153,6 @@
   "Loading photo...": "Foto wird geladen…",
   "Photo unavailable": "Foto nicht verfügbar",
   "Location obscured to a 0.2° cell": "Standort auf eine 0,2°-Rasterzelle verschleiert",
-  "Open on Acartia ↗": "Auf Acartia öffnen ↗",
   "Photo of {name}": "Foto von {name}",
   "Acartia": "Acartia",
   "CC BY 4.0": "CC BY 4.0",