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/partnership_offboard.sh

@@ -108,17 +108,7 @@ fi
 
 detect_hosts
 
-OWNER_ID="${PARTNERSHIP_OWNER_HOST:-HOST1}"
-MIRROR_ID=$( [[ "$OWNER_ID" == "HOST1" ]] && echo "HOST2" || echo "HOST1" )
-OWNER="${!OWNER_ID}"
-MIRROR="${!MIRROR_ID}"
-MIRROR_SSH_KEY="$SSH_KEY"
-OWNER_SSH_KEY="$SSH_KEY"
-
-AM_OWNER=false
-AM_MIRROR=false
-[[ "$MY_ID" == "$OWNER_ID" ]] && AM_OWNER=true
-[[ "$MY_ID" == "$MIRROR_ID" ]] && AM_MIRROR=true
+partnership_resolve_roles
 
 LOCAL_STATE_FILE="${STATE_DIR}/partnership_${LOCAL_SERVER_NAME}.db"
 REMOTE_STATE_FILE="${STATE_DIR}/partnership_${REMOTE_SERVER_NAME}.db"