Add persistent partner conf backup across reboots

conf_cache_save.sh runs first on array stop — snapshots partner confs from RAM
cache to /boot/config/varaverk/conf_bak/ before anything else shuts down.

conf_cache_restore.sh runs after conf_sync.sh on array start — if partner was
unreachable and RAM cache is incomplete, loads the backup into RAM then removes
it. Normal reboots: backup written, fresh pull succeeds, backup deleted unused.
Edge case (partner down at boot): backup fills the gap so fallback.sh has the
partner vars it needs to operate correctly.

Deployment/master.conf.template

@@ -292,6 +292,8 @@
 # Watchdogs (resource_watchdog, docker_watchdog, system_watchdog) are cronned via
 # watchdog_orchestrator.sh — NOT launched here.
     ARRAY_START_SCRIPTS=(
+        "System_Essentials/conf_sync.sh"              # pull partner confs + push own conf into /tmp/.vv/ RAM cache
+        "System_Essentials/conf_cache_restore.sh"     # load partner confs from persistent backup if conf_sync couldn't reach partner
         "Transcodes/ramdisk_setup.sh"                 # creates ramdisk + symlink before Emby starts
         "unRAID_Essentials/docker_syslog_filter.sh"   # suppress veth noise before logs fill
         "unRAID_Essentials/php_fpm_max_children.sh"   # WebGUI performance tuning
@@ -306,6 +308,7 @@
 # Run sequentially (foreground) — each must complete before the next starts.
 # Order matters: user scripts first (prevents new ops), then data movement, then containers.
     ARRAY_STOP_SCRIPTS=(
+        "System_Essentials/conf_cache_save.sh"          # snapshot partner conf RAM cache → /boot before anything stops
         "unRAID_Essentials/user_scripts_stop.sh"        # stop background scripts before they start new ops
         "Fallback/fallback.sh --stop"                   # gracefully stop fallback (not caught by user_scripts_stop)
         "unRAID_Essentials/rsync_stop.sh --rsync-only"  # kill rsync; skip container recovery (handled below)