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.

Partnership/ssh_setup.sh

@@ -74,9 +74,10 @@ acquire_lock
 detect_hosts
 
 # ── Derive key name from hostname ─────────────────────────────────────────────────────────────
-# Strip unraid- prefix (case-insensitive) if present → gmer4lfe_rsync_automation
-SHORT_NAME="${LOCAL_SERVER_NAME,,}"
-[[ "${SHORT_NAME}" == unraid-* ]] && SHORT_NAME="${SHORT_NAME:7}"
+# derive_short_name() title-cases the result (for display elsewhere) — lowercase it here,
+# same as before, since this feeds a filename → gmer4lfe_rsync_automation
+SHORT_NAME="$(derive_short_name "$LOCAL_SERVER_NAME")"
+SHORT_NAME="${SHORT_NAME,,}"
 SSH_KEY_NAME="${SHORT_NAME}_rsync_automation"
 SSH_KEY_PATH="/root/.ssh/${SSH_KEY_NAME}"
 SSH_PUB_PATH="${SSH_KEY_PATH}.pub"