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.

Deployment/master.conf.template

@@ -359,6 +359,7 @@
     CRITICAL_MAINTENANCE_SCRIPTS=(
         "Docker_Essentials/downloaders_reset.sh"        # clear stuck download states every 30min
         "Media/play_state_sync.sh"                      # sync watched/resume state across Emby + Jellyfin
+        "Arrs_Stack/arr_cache_prefill.sh ARR_PREFILL_WAIT_MINUTES=1"  # keep the shared arr tracked-data cache fresh — a live fetch+write takes seconds, not the boot-time 10min wait ceiling
     )
 
 # Shares synced every 30 minutes — defined per host in host*.conf.