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).

Fallback/fallback.sh

@@ -130,11 +130,13 @@
 # STATE FILES
 # ==============================================================================================
 #
-#   FALLBACK_STATE_FILE   — /boot/config/fallback_state.db (survives reboots)
+#   FALLBACK_STATE_FILE   — $STATE_DIR/fallback_state.db (survives reboots)
 #       Keys: state, fallback_start, handback_strikes, tier2_started,
 #       tier3_started, tier4_started, partnership_suspended, partner_lost_at.
-#       Lives on /boot/ intentionally — if the server was in FALLBACK when it
-#       rebooted, it resumes FALLBACK on restart.
+#       Survives reboots — $STATE_DIR is on the boot device (internal) or appdata
+#       (flash). Either way the array is up before this script runs, so the file
+#       is always accessible. If the server was in FALLBACK when it rebooted,
+#       it resumes FALLBACK on restart.
 #
 # ==============================================================================================
 # CONFIGURATION
@@ -185,7 +187,7 @@
 #       Consecutive remote-up checks required before handback begins. (default: 3)
 #
 #   FALLBACK_STATE_FILE
-#       State file path — /boot/config/fallback_state.db — survives reboots.
+#       State file path — $STATE_DIR/fallback_state.db — survives reboots.
 #
 #   FALLBACK_RSYNC_ENABLED
 #       Gate for writeback rsync jobs during handback. (default: true)
@@ -302,7 +304,7 @@ log "$ICON_GEAR Timeouts: docker=${DOCKER_TIMEOUT}s ssh=${SSH_TIMEOUT}s verify-w
 # ==============================================================================================
 # ── STATE FILE HELPERS ────────────────────────────────────────────────────────────────────────
 # ==============================================================================================
-# State file on /boot/config — survives reboots.
+# State file at $FALLBACK_STATE_FILE ($STATE_DIR/fallback_state.db) — survives reboots.
 # Format: key=value one per line.
 # Keys: state, fallback_start, handback_strikes, tier2_started, tier3_started, tier4_started