Wire up unused config vars found in follow-up audit pass

TRANSCODE_LOG_RETENTION was documented as trimming the daily transcode log
but never referenced — log grew unbounded. TRANSCODE_ORPHAN_AGE was shown in
--status but never used, so empty session folders were deleted immediately
instead of after the documented grace period, risking a race against ffmpeg
creating a folder just before writing its first segment.

docker_watchdog.sh's daemon-health thresholds were only hardcoded fallbacks
despite comments claiming they were master.conf-configurable, and it
referenced a heartbeat feature that was never implemented (that's owned by
watchdog_orchestrator.sh, its caller) — added the three thresholds to
master.conf for real and removed the stale heartbeat claim.

Also added the missing HOSTN_PARTNERSHIP_SERVICES_STACK block to
host.conf.template (containers.sh already read it via detect_hosts, just
never had a template entry) and corrected play_state_sync.sh's doc comment
for PLAY_SYNC_TYPES' actual default.

Transcodes/transcode_cleanup.sh

@@ -230,10 +230,11 @@ cleanup_location() {
 
     done < <(find "$location" -type f -mmin +"$max_age" 2>/dev/null)
 
-    # Remove empty directories — but NEVER remove transcoding-temp
-    # transcoding-temp must always exist on ramdisk so Emby finds it there first
+    # Remove empty directories older than TRANSCODE_ORPHAN_AGE — but NEVER remove
+    # transcoding-temp. Age gate avoids deleting a session folder ffmpeg just
+    # created but hasn't written its first segment into yet.
     if [[ "$DRY_RUN" == false ]]; then
-        find "$location" -mindepth 1 -type d -empty \
+        find "$location" -mindepth 1 -type d -empty -mmin +"${TRANSCODE_ORPHAN_AGE:-30}" \
             ! -name "transcoding-temp" -delete 2>/dev/null
     fi