Function append_see_more_button 

fn append_see_more_button<F: Fn() + 'static>(
    grid: &FlowBox,
    remaining: usize,
    on_expand: F,
)

Append a card-sized “See More” tile to a FlowBox grid.

Matches the dimensions of adjacent explore tiles so the button fills a full card slot rather than appearing as a small inline text link.