Structural reorganization: watchdog taxonomy + server_reboot integration

Watchdog renames and moves:
  system_watchdog.sh → stability_watchdog.sh (last line of defense — reboots)
  storage_watchdog.sh → Watchdogs/System/storage_watchdog.sh
  webgui_restart.sh → Watchdogs/System/webgui_watchdog.sh (renamed to match folder convention)

New thin orchestrator:
  Watchdogs/system_watchdog.sh — runs SYSTEM_WATCHDOG_SCRIPTS from master.conf
  Sits between docker_watchdog and stability_watchdog in the orchestrator tier chain
  System/ subfolder is the growth seam for future system component watchdogs

master.conf:
  WATCHDOG_ORCHESTRATOR_SCRIPTS updated — storage removed, system_watchdog added as tier
  SYSTEM_WATCHDOG_SCRIPTS array added — storage + webgui

server_reboot.sh:
  Calls array_stopping.sh before VM shutdown for guaranteed safe array stop
  Removed raw rc.docker stop and exit trap — orchestrator owns container shutdown

README-User_Script_Plug-in.md

@@ -1201,23 +1201,23 @@ flip count, session split ramdisk vs SSD).
 ## ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 
 > **system_watchdog.sh is started by array_start.sh — not scheduled separately.**
-> **webgui_restart.sh, system_tuning_monitor.sh, clear_logs.sh are scheduled below.**
+> **webgui_watchdog.sh, system_tuning_monitor.sh, clear_logs.sh are scheduled below.**
 > **inotify_tuning.sh, php_fpm_max_children.sh, docker_syslog_filter.sh run via array_start.sh.**
 
 ---
 
-### ── webgui_restart ───────────────────────────────────────────────────────────
+### ── webgui_watchdog ───────────────────────────────────────────────────────────
 
 ```
 Category:   unRAID_Essentials
-Name:       webgui_restart
+Name:       webgui_watchdog
 Schedule:   */10 * * * *  (every 10 minutes)
 Background: YES
 ```
 
 ```bash
 #!/bin/bash
-/mnt/user/appdata/unraid_scripts/unRAID_Essentials/webgui_restart.sh
+/mnt/user/appdata/unraid_scripts/Watchdogs/System/webgui_watchdog.sh
 ```
 
 **What it does:**
@@ -1275,7 +1275,7 @@ Background: NO
 
 ```bash
 #!/bin/bash
-/mnt/user/appdata/unraid_scripts/Watchdogs/system_watchdog.sh --status
+/mnt/user/appdata/unraid_scripts/Watchdogs/stability_watchdog.sh --status
 ```
 
 **What it shows:**
@@ -1650,7 +1650,7 @@ At Startup of Array:
   transcode_management                 BG: YES — cleanup then manager
 
 */10 * * * *  (every 10 min):
-  webgui_restart                       BG: YES — silent when healthy
+  webgui_watchdog                       BG: YES — silent when healthy
 
 */15 * * * *  (every 15 min):
   critical_sync_maintenance            BG: YES — auth stack + Emby dirty + partnership check