Add ping endpoint, update-refresh prompt, and dark-mode polish

resources/lang/de.json

@@ -186,6 +186,9 @@
   "version.up_to_date": "Aktuell",
   "version.update_available": "Update verfügbar (v{{version}})",
   "version.update_available_short": "Update verfügbar",
+  "version.refresh_prompt_title": "Update verfuegbar",
+  "version.refresh_prompt_body": "Ein neuerer Build ({{build}}) ist verfuegbar. Jetzt neu laden, um die aktuelle Version zu verwenden?",
+  "version.remind_later": "Spaeter",
   "version.unknown": "Version unbekannt",
   "version.update_now": "Jetzt aktualisieren",
   "version.update_title": "System aktualisieren",

resources/lang/en.json

@@ -176,6 +176,9 @@
   "version.up_to_date": "Up to date",
   "version.update_available": "Update available (v{{version}})",
   "version.update_available_short": "Update available",
+  "version.refresh_prompt_title": "Update available",
+  "version.refresh_prompt_body": "A newer build ({{build}}) is available. Refresh now to load the latest version?",
+  "version.remind_later": "Later",
   "version.unknown": "Version unknown",
   "version.update_now": "Update now",
   "version.update_title": "Update system",