Generalize tracked-data cache from Lidarr-only to all three arrs

Shared cache/rescan-duration logic in common.sh now takes an arr_type
param instead of being Lidarr-specific, so Sonarr and Radarr cleanup
scripts get the same cache-first fetch + rescan-aware retry Lidarr had.
Avoids redundant full-library API calls across scripts run back to back,
and stops false failures when a fetch lands mid-rescan.

Arrs_Stack/lidarr_duplicate_artist_cleanup.sh

@@ -134,7 +134,7 @@ trap 'rm -rf "$TMP_DIR"' EXIT
 # ━━━ Fetch Artists (cache-aware — waits out an active rescan rather than trusting a
 # mid-scan number, falls back to cache if Lidarr's still busy after the strike limit) ━━━
 # ==============================================================================================
-ARTISTS=$(lidarr_get_tracked_data "$LIDARR_URL" "$LIDARR_API_KEY" "v1")
+ARTISTS=$(arr_get_tracked_data "lidarr" "$LIDARR_URL" "$LIDARR_API_KEY" "v1")
 if [[ -z "$ARTISTS" ]]; then
     warn "Lidarr busy and no usable cache — deferring to next scheduled run"
     exit 0