Remove remaining OS-specific hardcodes from core scripts

OS version reads now go through platform_get_os_version() and
platform_os_version_probe_cmd() instead of grepping /etc/unraid-version directly.

STATE_DIR fallbacks to /boot/config removed — STATE_DIR is always set by
load_config.sh and the fallback encoded a platform-specific path.

Setup DB path references use platform_setup_db_path() instead of the
VARAVERK_SETUP_FILE/-/boot/config compound fallback.

DOCKER_APPDATA_BASE default removed from arr_sync.sh — the adapter sets it.

Fallback/fallback.sh

@@ -345,7 +345,7 @@ state_init() {
 # Returns 0 (true) if the local partnership DB reports an ACTIVE partnership.
 # Reads /boot/config/partnership_<hostname>.db — no subprocess, no SSH.
 check_partnership_active() {
-    local state_file="${STATE_DIR:-/boot/config}/partnership_${LOCAL_SERVER_NAME}.db"
+    local state_file="${STATE_DIR}/partnership_${LOCAL_SERVER_NAME}.db"
     local state
     state=$(grep "^state=" "$state_file" 2>/dev/null | cut -d= -f2)
     [[ "$state" == "ACTIVE" ]]
@@ -603,13 +603,13 @@ if [[ "$SHOW_STATUS" == true ]]; then
     TIER4=$(state_get tier4_started)
     STRIKES=$(state_get handback_strikes)
 
-    local_ver=$(grep -oP '(?<=version=")[^"]+' /etc/unraid-version 2>/dev/null || echo "unknown")
+    local_ver=$(platform_get_os_version 2>/dev/null || echo "unknown")
 
     echo ""
     echo "━━━━━ $ICON_SUMMARY FALLBACK STATUS ━━━━━"
     echo "$ICON_HOST    My ID:       $MY_ID ($LOCAL_SERVER_NAME)"
     echo "$ICON_HOST    Remote ID:   $REMOTE_ID ($REMOTE_SERVER_NAME — $REMOTE_SERVER)"
-    echo "$ICON_GEAR    unRAID ver:  $local_ver"
+    echo "$ICON_GEAR    OS ver:      $local_ver"
     echo "$ICON_FALLBACK State:      $CURRENT_STATE"
     echo "$ICON_NET     Local DDNS:  ${LOCAL_DDNS_CONTAINERS[*]:-none}"
     echo "$ICON_NET     Remote DDNS: ${REMOTE_DDNS_CONTAINERS[*]:-none}"