* fix: session secret key, cart session persistence, null variation attributes
- Use wp_salt() as fallback secret key instead of hardcoded 24-byte string
to satisfy php-jwt v7's HS256 minimum key length requirement (Closes#1009)
- Call get_cart_from_session() after wc_load_cart() in
initialize_session_and_cart() to prevent cart queries from clearing
persisted session data (Closes#1010)
- Guard against null $attrs in variation_attributes_to_data_array()
to prevent PHP warnings when variations have no attributes (Closes#1011)
- Return empty array instead of null for product attribute options
when no terms exist
* chore: Linter compliances met
