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.

Transcodes/transcode_manager.sh

@@ -298,6 +298,7 @@ RAMDISK_HEALTHY=true
 SSD_HEALTHY=true
 EMBY_RUNNING=true
 SOMETHING_HAPPENED=false   # controls whether summary is printed
+ERROR_OCCURRED=false       # controls exit code
 
 # ── Check 1 — Emby running ───────────────────────────────────────────────────────────────────
 if [[ "$TRANSCODE_CHECK_EMBY" == true ]]; then
@@ -345,6 +346,7 @@ if ! mountpoint -q "$RAMDISK_PATH" 2>/dev/null; then
     error "Ramdisk not mounted at $RAMDISK_PATH"
     RAMDISK_HEALTHY=false
     SOMETHING_HAPPENED=true
+    ERROR_OCCURRED=true
     if [[ "$DRY_RUN" == false ]]; then
         warn "Flipping symlink to SSD — ramdisk unavailable"
         flip_symlink "$TRANSCODE_SSD" "ramdisk disappeared"
@@ -544,6 +546,7 @@ case "$TRANSCODE_MANAGER_MODE" in
             notify "Transcode ramdisk mode failed on $(hostname) ($MY_ID) — ramdisk not mounted" \
                 "Transcode Manager" "warning"
             SOMETHING_HAPPENED=true
+            ERROR_OCCURRED=true
         else
             if [[ "$CURRENT_TARGET" != "$RAMDISK_PATH" ]]; then
                 flip_symlink "$RAMDISK_PATH" "ramdisk mode"
@@ -565,6 +568,7 @@ case "$TRANSCODE_MANAGER_MODE" in
         if [[ "$SSD_HEALTHY" == false ]]; then
             error "SSD mode selected but SSD path is not available"
             SOMETHING_HAPPENED=true
+            ERROR_OCCURRED=true
         else
             if [[ "$CURRENT_TARGET" != "$TRANSCODE_SSD" ]]; then
                 flip_symlink "$TRANSCODE_SSD" "ssd mode"
@@ -591,11 +595,13 @@ case "$TRANSCODE_MANAGER_MODE" in
                     notify "Transcode ramdisk full on $(hostname) ($MY_ID) and SSD unavailable" \
                         "Transcode Manager" "warning"
                     SOMETHING_HAPPENED=true
+                    ERROR_OCCURRED=true
                 else
                     SSD_FREE_GB=$(get_ssd_free_gb)
                     if (( $(awk "BEGIN {print ($SSD_FREE_GB < $RAMDISK_SSD_MIN_GB) ? 1 : 0}") )); then
                         warn "SSD only ${SSD_FREE_GB}GB free — below ${RAMDISK_SSD_MIN_GB}GB minimum, not flipping"
                         SOMETHING_HAPPENED=true
+                        ERROR_OCCURRED=true
                     else
                         warn "Ramdisk ${RAMDISK_USED_GB}GB — above ${RAMDISK_WARN_GB}GB, flipping to SSD"
                         flip_symlink "$TRANSCODE_SSD" "threshold exceeded"
@@ -659,4 +665,7 @@ if [[ "$SOMETHING_HAPPENED" == true ]]; then
     echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
 else
     echo "Transcode manager — all healthy — $MY_ID ($(format_duration $(( END - START ))))"
-fi
+fi
+
+[[ "$ERROR_OCCURRED" == true ]] && exit 1
+exit 0