Adds a 'Season taxonomy' setting (default empty) that points at an existing taxonomy registered against the destination post type. On every successful import the plugin reads itunes:season, looks up (or creates) a term with that numeric name in the configured taxonomy, and assigns it to the imported post via wp_set_object_terms. Behavior: - Empty option: no-op. Existing posts and installs without a season taxonomy are unaffected. - Tax that doesn't exist or isn't attached to the post type: no-op. - Feed item with no itunes:season: no-op. Manual taxonomy assignments are preserved on subsequent refreshes. - Otherwise: the feed value wins, on both create and update paths. The new assign_season_term() helper is public so it is unit-testable, and four smoke tests cover the lookup, create-on-miss, unconfigured, and no-season paths.