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).

Monitors/Manual-Monitors.md

@@ -151,14 +151,14 @@ BACKUP_VERIFY_MIN_SIZE="1M"   # skip files smaller than this
 
 ```bash
 # master.conf
-BANDWIDTH_LOG="/boot/config/bandwidth_history.db"   # survives reboots
+BANDWIDTH_LOG="$DATA_DIR/bandwidth_history.db"   # survives reboots
 BANDWIDTH_LOG_RETENTION=90    # days — file stays bounded, never grows unbounded
 BANDWIDTH_WARN_GB=50          # flag transfers or daily totals exceeding this
 ```
 
-**Why `/boot/config/`**: The log needs to survive reboots to build a useful history.
-`/boot/config/` is on the USB flash drive, which survives reboots and is backed up
-by unRAID's flash backup. The log is bounded by `BANDWIDTH_LOG_RETENTION` so it never
+**Why `$DATA_DIR`**: The log needs to survive reboots to build a useful history.
+`$DATA_DIR` (`$SCRIPTS_DIR/data/`) is on the boot device (internal) or appdata (flash),
+both of which survive reboots. The log is bounded by `BANDWIDTH_LOG_RETENTION` so it never
 grows unbounded.
 
 **`BANDWIDTH_WARN_GB`**: Set to a value that represents "unexpectedly large" for your
@@ -401,7 +401,7 @@ BACKUP_VERIFY_SAMPLE=10
 BACKUP_VERIFY_MIN_SIZE="1M"
 
 # bandwidth_monitor.sh
-BANDWIDTH_LOG="/boot/config/bandwidth_history.db"
+BANDWIDTH_LOG="$DATA_DIR/bandwidth_history.db"
 BANDWIDTH_LOG_RETENTION=90
 BANDWIDTH_WARN_GB=50