Function humanize_number 

pub fn humanize_number(n: f64) -> String

Humanize a number into a compact display string:

input	output
42.0	"42"
1_234.5	"1,234.50"
12_438.2	"12.4K"
1_500_000.0	"1.50M"
2_700_000_000.	"2.70B"

Suitable for card values where horizontal space is scarce.