Make all arr library-list fetches cache-first with live fallback

Every script that fetches the full Lidarr/Sonarr/Radarr tracked-library
list now goes through arr_get_tracked_data() instead of hitting the API
directly -- cache-first when fresh, live fetch as fallback when stale,
waits out an active rescan before either. Per-item file data (trackFile/
episodefile/moviefile) stays live-only everywhere, since that's the
actual disk-truth these scripts' decisions depend on and was never part
of what's cached.

Also adds arr_cache_prefill.sh to CRITICAL_MAINTENANCE_SCRIPTS (30min
tier) with a short 1min wait ceiling, so the cache stays consistently
fresh instead of only refreshing whenever some other script happens to
write through. A full cache refresh for all three arrs measured at ~12s
total live -- nothing like the multi-hour cost of an actual rescan.

Arrs_Stack/lidarr_missing_art.sh

@@ -254,10 +254,10 @@ echo ""
 echo "━━━ $ICON_SYNC Building Album Directory Map ━━━"
 
 declare -A ALBUM_DIR_MAP
-_artist_list=$(curl_json "$LIDARR_URL/api/v1/artist?apikey=$LIDARR_API_KEY")
-# Write-through — keeps the shared tracked-data cache fresh as a side effect of a fetch
-# this script already needed for its own purposes. See arr_get_tracked_data() in common.sh.
-arr_cache_write "lidarr" "$_artist_list"
+# Cache-first — arr_get_tracked_data() serves the shared cache when it's fresh (now kept
+# current every 30min by arr_cache_prefill.sh in CRITICAL_MAINTENANCE_SCRIPTS), falls back to
+# a live fetch when it's stale, and waits out an active rescan before either.
+_artist_list=$(arr_get_tracked_data "lidarr" "$LIDARR_URL" "$LIDARR_API_KEY" "v1")
 _map_artist_count=$(echo "$_artist_list" | jq '. | length')
 info "Fetching track files for $_map_artist_count artists..."
 
@@ -364,7 +364,9 @@ info "Checked: $ALBUMS_CHECKED | Complete: $ALBUMS_COMPLETE | Needed art: $ALBUM
 echo ""
 echo "━━━ $ICON_EMBY Artists ━━━"
 
-artists=$(curl_json "$LIDARR_URL/api/v1/artist?apikey=$LIDARR_API_KEY")
+# Cache-first — see the earlier album-map fetch above for why (arr_get_tracked_data serves
+# the shared cache when fresh, live fetch as fallback, waits out an active rescan first).
+artists=$(arr_get_tracked_data "lidarr" "$LIDARR_URL" "$LIDARR_API_KEY" "v1")
 
 if [[ -z "$artists" || "$artists" == "null" ]]; then
     error "Lidarr artist API returned empty — aborting"