v1.0.1 - rename prefix to ans_spd_ to avoid a fatal collision with the ticketing bridge

No behaviour change. ars-nova-ticketing-bridge already owns the ans_sp_ prefix for season PROJECTS (ans_sp_render, ans_sp_place, ans_sp_date_range, ans_sp_styles, ans_sp_event_term). Neither plugin guards its declarations with function_exists, and this plugin loads first alphabetically, so any future ans_sp_ name added to the bridge would fatal it on every request. The bridge is the incumbent and is in active parallel development, so this plugin moved to ans_spd_ instead. Ten functions, two constants and the cart-item key renamed; the header and README record why it must not be tidied back.