doc audit — fix stale watchdog vars, fallback_state_reset, add monthly_maintenance and mesh_monitor sections

- Tools/Manual-Tools.md: fallback_state_reset.sh marked not yet built; manual
  workaround added; TOC entry updated; failover→fallback rename throughout
- Watchdogs/Manual-Watchdogs.md: System Watchdog config block updated — remove
  pre-split vars (MEM_WARN_GB, MEM_SHUTDOWN_GB, MEM_GB, MEM_RECOVER_GB,
  SYS_WATCHDOG_MEM_SHUTDOWN_EXCLUDED, SYS_WATCHDOG_REQUIRED_CONTAINERS);
  add SYS_WATCHDOG_MEM_GB (reboot trigger only); fix state file path names
  (watchdog_state.db → container_watchdog_state.db,
  sys_watchdog_state.db → system_watchdog_state.db)
- Orchestrators/README-Orchestrators.md: add monthly_maintenance.sh section
  with two-gate model, configuration reference, and usage examples
- Monitors/README-Monitors.md: add mesh_monitor.sh to both tables and diagram
- Monitors/Manual-Monitors.md: add mesh_monitor.sh section
- README-User_Script_Plug-in.md, Rsync/README-Rsync.md, Rsync/Manual-Rsync.md,
  README.md: emby-failover → emby-fallback (missed from prior batch)

Watchdogs/Manual-Watchdogs.md

@@ -652,10 +652,8 @@ WATCHDOG_RESTART_CRASHED=true
 WATCHDOG_BATCH_NOTIFY=true
 
 # State files:
-WATCHDOG_STATE_FILE="/tmp/watchdog_state.db"
-SYS_WATCHDOG_FAILED_FILE="/boot/config/system_watchdog_failed.db"
+WATCHDOG_STATE_FILE="/tmp/container_watchdog_state.db"
 WATCHDOG_CONTAINER_RESTART_LOG="/boot/config/container_restart_history.db"
-SYS_WATCHDOG_STATE_FILE="/tmp/sys_watchdog_state.db"
 
 # host*.conf
 HOST1_WATCHDOG_CONTAINERS=()          # "ContainerName:LimitMB"
@@ -679,6 +677,8 @@ STORAGE_WATCHDOG_STATE_FILE="/tmp/storage_watchdog_state.db"
 # )
 
 # ── System Watchdog ────────────────────────────────────────────────────────────
+# Reboot trigger only — warn/shutdown/recover RAM tiers handled by resource_watchdog.sh
+# RW_RAM_HARD_GB > SYS_WATCHDOG_MEM_GB always (resource_watchdog acts before watchdog reboots)
 SYS_WATCHDOG_STRIKE_LIMIT=2
 SYSTEM_WATCHDOG_INTERVAL=300
 
@@ -686,10 +686,7 @@ SYS_WATCHDOG_REBOOT_WINDOW_HRS=2
 SYS_WATCHDOG_MAX_REBOOTS=3
 SYS_WATCHDOG_OOM_LIMIT=3
 
-MEM_WARN_GB=10
-MEM_SHUTDOWN_GB=6
-MEM_GB=4
-MEM_RECOVER_GB=30
+SYS_WATCHDOG_MEM_GB=4              # strike system → reboot (last resort — below resource_watchdog hard stop)
 
 SYS_WATCHDOG_ROOTFS_CRITICAL_PCT=99
 SYS_WATCHDOG_FD_CRITICAL_PCT=95
@@ -703,13 +700,8 @@ SYS_WATCHDOG_ABORT_ON_ZFS_UNHEALTHY=true
 SYS_WATCHDOG_ABORT_ON_PARITY=true
 SYS_WATCHDOG_ABORT_ON_MOVER=true
 
-SYS_WATCHDOG_MEM_SHUTDOWN_EXCLUDED=(
-    "NginxProxyManager" "Authelia" "Mariadb" "Redis" "Emby" "Dispatcharr"
-)
-SYS_WATCHDOG_REQUIRED_CONTAINERS=()
-
 # State files:
-SYS_WATCHDOG_STATE_FILE="/tmp/sys_watchdog_state.db"
+SYS_WATCHDOG_STATE_FILE="/tmp/system_watchdog_state.db"
 SYS_WATCHDOG_FAILED_FILE="/boot/config/system_watchdog_failed.db"
 SYS_WATCHDOG_REBOOT_LOG="/boot/config/system_watchdog_reboots.db"
 SYS_WATCHDOG_OOM_FILE="/tmp/system_watchdog_oom.db"