Viewbox goes from 300x96 to 1200x240 with aspect-[5/1] so the SVG
fills the card instead of shrinking to a ~300 px strip. Fonts,
gridlines (0/25/50/75/100), and point markers scale up to match,
and the x-axis now shows up to 7 evenly spaced hour labels instead
of just start/middle/end.