Storage-mode awareness pass + doc update for System_Essentials through Partnership

All state/data file paths in scripts and PHP now resolve via STATE_DIR / DATA_DIR /
PERSISTENT_CONF_CACHE instead of hardcoded /boot/config/ or /tmp/ paths, so the
ecosystem works in both internal and appdata storage modes.

PHP layer (watchdog.php, partnership.php, fallback.php, monitor.php, snapshot.php,
config.php): all state reads switched to STATE_DIR constant; remote state reads use
the new vv_remote_state_cmd() helper which resolves the remote's SCRIPTS_DIR via
their varaverk.cfg before building the path.

conf_sync.sh: fixed SCRIPTS_ROOT → SCRIPTS_DIR bug on MY_CONF path; added
_remote_scripts_dir() to resolve partner's SCRIPTS_DIR before SCP pull.

fallback.php page: added controls card (PARTNERSHIP_ENABLED, FALLBACK_ENABLED,
FALLBACK_RSYNC_ENABLED toggles), status grid, and settings card.

README and Manual updated for System_Essentials, Watchdogs, Fallback, Rsync,
Media, Monitors, Orchestrators, Partnership: added new scripts (conf_sync,
conf_cache_save/restore, conf_cache_watchdog, play_state_sync, start_webhook_listener,
upgrade_webhook_handler), corrected all stale /boot/config/ state file paths to
$STATE_DIR/$DATA_DIR, noted webgui/php_fpm/mover/user_scripts scripts moved to
Plugin/unraid/System_Essentials, fixed start_webhook_listener.sh header (Node.js,
not PHP -S).

Docker_Essentials/README-Docker_Essentials.md

@@ -139,7 +139,7 @@ happens after an update, and you want to know when it does.
 A container keeps appearing in a broken state. You SSH in and see it's stopped. You
 don't know if the watchdog tried to restart it and failed, gave up and skip-listed it,
 is mid-attempt right now, or hasn't noticed yet. You have to manually check the skip
-list file on `/boot/config/`, check the restart history file, check the state file —
+list file in `$STATE_DIR`, check the restart history file, check the state file —
 none of which have obvious formats.
 
 The fix: `watchdog_skip_list_manager.sh` (in `Tools/`). One command to see exactly what's