feat: slskd reconnect guard in downloaders_reset, mass v2 sync

- downloaders_reset: connection check block before slskd API sections;
  triggers PUT /api/v0/server reconnect if disconnected, polls 60s,
  gates Stuck Searches and Dead Transfer Records on SLSKD_CONNECTED
- Sync all modified/new/deleted files from v2 refactor across Docker_Essentials,
  Media, Monitors, Partnership, Rsync, Tools, Transcodes, unRAID_Essentials,
  common.sh, master confs, and new Manual/README docs

master_host2.conf

@@ -99,6 +99,28 @@
         # "NginxProxyManager|81"
     )
 
+# Containers to stop on this server before the owner deploys the auth stack during onboard.
+# List whatever auth/proxy containers are currently running here.
+    HOST2_PARTNERSHIP_REPLACE_CONTAINERS=(
+        "NginxProxyManager"
+        "Authelia"
+        "Authelia-Secondary"
+        "Mariadb-Authelia"
+        "Mariadb-Authelia-Secondary"
+        "Redis-Authelia"
+        "Redis-Authelia-Secondary"
+        "Lldap"
+    )
+
+# Arr containers to stop on this server before the owner deploys the arr stack during onboard.
+    HOST2_PARTNERSHIP_ARR_REPLACE_CONTAINERS=(
+        # "Sonarr"
+        # "Radarr"
+        # "Lidarr"
+        # "Prowlarr"
+        # "Bazarr"
+    )
+
 # Paths HOST1 should collect during the grace window after offboard.
 # Notified on offboard — no auto-deletion, HOST1 must collect manually within PARTNERSHIP_GRACE_HOURS.
     HOST2_PARTNERSHIP_MIRROR_BACKUPS=(