Fix dead/incorrect vars and consolidate duplicated logic into common.sh

Codebase-wide audit pass: fixed real bugs (SSH hangs missing BatchMode,
local-outside-function no-ops, variable name collisions, a truncated
ratio calc, wrong state-dir path, DARK vs NO_INTERNET drift, and more),
then pulled logic that was duplicated across multiple scripts — arr
cleanup safety gates, docker restart ordering, container maintenance
stop/restart, watchdog state-file helpers, partnership role resolution,
cert expiry checks, remote node discovery, and TMDB discovery scoring —
into common.sh so each now has a single implementation.

Arrs_Stack/arr_sync.sh

@@ -206,13 +206,7 @@ declare -A _ID_TYPE=([lidarr]="string" [sonarr]="int" [radarr]="int")
 ARR_TYPES=(lidarr sonarr radarr)
 
 # ── Remote node discovery ──────────────────────────────────────────────────────────────────────
-REMOTE_NODES=()
-for _hv in HOST1 HOST2 HOST3 HOST4 HOST5 HOST6 HOST7 HOST8; do
-    [[ "$_hv" == "$MY_ID" ]] && continue
-    [[ -z "${!_hv:-}" ]] && continue
-    REMOTE_NODES+=("$_hv")
-done
-unset _hv
+discover_remote_nodes
 
 if [[ "${#REMOTE_NODES[@]}" -eq 0 ]]; then
     warn "No remote nodes defined in master.conf — nothing to sync"
@@ -478,7 +472,7 @@ if [[ "$SHOW_STATUS" == true ]]; then
     echo ""
     echo "  Arr    Port  URL"
     for _arr in "${ARR_TYPES[@]}"; do
-        local _url="" _key=""
+        _url=""
         case "$_arr" in
             lidarr) _url="${LIDARR_URL:-not configured}" ;;
             sonarr) _url="${SONARR_URL:-not configured}" ;;
@@ -992,8 +986,8 @@ _sync_arr() {
             fi
         fi
 
-        local _n_local=${#to_add_local[@]:-}; _n_local=${_n_local:-0}
-        local _n_remote=${#to_add_remote[@]:-}; _n_remote=${_n_remote:-0}
+        local _n_local=${#to_add_local[@]}
+        local _n_remote=${#to_add_remote[@]}
         log "  $node_name: +${_n_local} local | +${_n_remote} remote | $total_skipped blocklisted"
 
         unset remote_ids to_add_local to_add_remote _n_local _n_remote