Ship MEDIA_SEED_ENABLED off by default so a fresh node never inherits a multi-week transfer

Onboard arms the other Tier 2 gates but not this one — free space on a just-onboarded partner is the thing nobody has checked yet.

Deployment/master.conf.template

@@ -648,6 +648,13 @@
 # partner is going to be filled some other way (a physically moved disk, an existing library),
 # and onboard will finish without ever starting it. Turning it back on does not start anything
 # by itself; dispatch it from the Partnership tab or run the script.
+#
+#   NOTE ON THE DEFAULT: this one ships OFF, and unlike Tier 1 it is not armed by a successful
+#   onboard — Step 9c arms RSYNC_ENABLED, CONF_SYNC_ENABLED and ARR_SYNC_ENABLED, and
+#   deliberately not this. Seeding a partner is a decision about weeks of bandwidth and tens of
+#   terabytes of disk, and the node that has just been onboarded is exactly the node nobody has
+#   checked the free space on yet. Arm it when you have decided the partner should be filled by
+#   rsync rather than by hand. Turning it on is one switch; noticing it was on is not.
 #   → Run individual: bash Rsync/rsync.sh /mnt/user/Movies
 #   → When ready: INTERMEDIATE_RSYNC_ENABLED=true  DAILY_RSYNC_ENABLED=true
 #   NOTE ON THE DEFAULT: Tier 1 ships OFF. This template is what a brand-new node is seeded from
@@ -663,7 +670,7 @@
     WEEKLY_RSYNC_ENABLED=true           # Tier 2 — weekly_sync_maintenance.sh rsync section
     MONTHLY_RSYNC_ENABLED=true          # Tier 2 — monthly_maintenance.sh rsync section
     FALLBACK_RSYNC_ENABLED=true         # Tier 2 — fallback.sh writeback jobs on handback
-    MEDIA_SEED_ENABLED=true             # Tier 2 — Rsync/media_seed.sh, the onboard first-fill
+    MEDIA_SEED_ENABLED=false            # Tier 2 — Rsync/media_seed.sh, the onboard first-fill
 
 # ━━━ Download Webhook ━━━
 # Immediate push to remote nodes on every Sonarr/Radarr/Lidarr Download event.