Fix dead-variable and exit-code bugs found in codebase-wide audit

Same audit as the orchestrator standardization pass (2a062e5), extended to
every remaining script. Found the same class of bug independently recurring:
ramdisk_stop.sh checked $LOG (nothing assigns it, should be $ENABLE_LOGGING),
partnership_onboard.sh checked $LOG_MODE (same issue), emby_session_report.sh
checked $TRANSCODE_PCT which was never computed so the high-transcode alert
could never fire, and storage_migrate.sh never called detect_hosts() so
$MY_ID was empty, silently breaking the post-migration host*.conf update.
partnership_manager.sh used `local` at top-level script scope (invalid outside
a function) and had two master.conf path references missing "Configurations/".

Along the way: several scripts (share_setup.sh, conf_sync.sh,
downloaders_reset.sh, transcode_cleanup.sh, transcode_manager.sh,
remote_arr_cache_writer.sh, upgrade_webhook_handler.sh) had no explicit
trailing exit code, so they always reported success regardless of real
failures. play_state_sync.sh was missing the partnership gate its own header
documented, so remote play-state sync ran even with PARTNERSHIP_ENABLED=false;
it also always exited 0 on sync errors. arr_profile_enforcer.sh and
webhook_setup.sh hand-rolled their own flag parsing instead of common.sh's
parse_args, so --log silently did nothing on either.

system_watchdog.sh was itself an un-standardized mini-orchestrator — converted
to the shared run_orch_child()/JOB_PASS/JOB_FAIL pattern, added the missing
failure notification, and fixed dry-run to pass --dry-run down to children
instead of skipping them outright. Also fixed a stale webgui_watchdog.sh path
in master.conf.template that would break system_watchdog.sh on any fresh
install.

Closed a sibling-drift gap: radarr_cleanup.sh and sonarr_cleanup.sh were
missing lidarr_cleanup.sh's tracked-count percentage-drop safety gate and its
"not configured on this host, skip cleanly" guard — both now match Lidarr's
7-gate model.

Monitors/emby_session_report.sh

@@ -218,6 +218,9 @@ TRANSCODE_NOW=$(echo "$SESSIONS" | \
     2>/dev/null || echo 0)
 DIRECT_NOW=$(( ACTIVE_COUNT - TRANSCODE_NOW ))
 
+TRANSCODE_PCT=0
+[[ "$ACTIVE_COUNT" -gt 0 ]] && TRANSCODE_PCT=$(( TRANSCODE_NOW * 100 / ACTIVE_COUNT ))
+
 echo "  $ICON_EMBY Active streams:  $ACTIVE_COUNT"
 echo "  $ICON_EMBY Direct play:     $DIRECT_NOW"
 echo "  $ICON_EMBY Transcoding:     $TRANSCODE_NOW"
@@ -333,7 +336,7 @@ END=$(date +%s)
 echo "━━━━━ $ICON_SUMMARY EMBY REPORT SUMMARY ━━━━━"
 echo "$ICON_HOST    Identity:  $MY_ID ($LOCAL_SERVER_NAME)"
 echo "$ICON_EMBY    Server:    $SERVER_NAME (v$SERVER_VERSION)"
-echo "$ICON_EMBY    Active:    $ACTIVE_COUNT streams ($DIRECT_NOW direct / $TRANSCODE_NOW transcode)"
+echo "$ICON_EMBY    Active:    $ACTIVE_COUNT streams ($DIRECT_NOW direct / $TRANSCODE_NOW transcode, ${TRANSCODE_PCT}%)"
 echo "$ICON_EMBY    Library:   $MOVIE_COUNT movies  $EPISODE_COUNT episodes  $SONG_COUNT songs"
 echo "$ICON_EMBY    Period:    $TOTAL_PLAYS play events in last ${EMBY_REPORT_DAYS} days"
 echo "$ICON_TIME    Duration:  $(format_duration $(( END - START )))"
@@ -341,7 +344,7 @@ echo "━━━━━━━━━━━━━━━━━━━━━━━━
 
 # Only notify on issues — high transcode rate may indicate config problem
 if [[ "$DRY_RUN" == false ]]; then
-    if [[ "$TOTAL_PLAYS" -gt 10 && "${TRANSCODE_PCT:-0}" -gt 80 ]]; then
+    if [[ "$TOTAL_PLAYS" -gt 10 && "$TRANSCODE_PCT" -gt 80 ]]; then
         notify "Emby report on $(hostname) — high transcode rate: ${TRANSCODE_PCT}% of $TOTAL_PLAYS plays — check direct play config" \
             "Emby Report" "warning"
     fi