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).

Configurations/master.conf

@@ -123,6 +123,7 @@
 #                Requirement: ALL state files MUST use $STATE_DIR. No /tmp, no /boot/config root.
     DATA_DIR="${SCRIPTS_DIR}/data"
     STATE_DIR="${SCRIPTS_DIR}/State_Files"
+    PERSISTENT_CONF_CACHE="${SCRIPTS_DIR}/.cache/vv/d"
 
 # ── Version Parity ──
 # Controls behaviour when local and remote unRAID versions differ.
@@ -295,7 +296,7 @@
 # watchdog_orchestrator.sh — NOT launched here.
     ARRAY_START_SCRIPTS=(
         "Plugin/unraid/System_Essentials/unraid_api_key_renew.sh"   # re-register Varaverk API key — registry is ephemeral
-        "System_Essentials/conf_sync.sh"              # pull partner confs + push own conf into /tmp/.vv/ RAM cache
+        "System_Essentials/conf_sync.sh"              # pull partner confs + push own conf into /tmp/.cache/vv/d/ 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
         "System_Essentials/docker_syslog_filter.sh"   # suppress veth noise before logs fill