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.

Rsync/rsync.sh

@@ -180,7 +180,7 @@ if ! check_rsync_enabled; then
 fi
 
 # Blocklist gate — refuse to sync with a partner blocked after offboard
-BLOCKLIST_FILE="${PARTNERSHIP_BLOCKLIST_FILE:-${STATE_DIR:-/boot/config}/partnership_blocklist.db}"
+BLOCKLIST_FILE="${PARTNERSHIP_BLOCKLIST_FILE:-${STATE_DIR}/partnership_blocklist.db}"
 if [[ -f "$BLOCKLIST_FILE" ]] && grep -q "^${REMOTE_SERVER_NAME}|" "$BLOCKLIST_FILE" 2>/dev/null; then
     error "Rsync blocked — $REMOTE_SERVER_NAME is on the partnership blocklist"
     error "Re-onboard the partnership to restore access: partnership_manager.sh --onboard"