Unifies PNG and SVG body-part images behind a single CSS-mask
render path, so both now colorize with a --accent CSS variable.
Accent splits by measurement type: --blue for proportion parts
(chest, shoulders, waist, hips) and --nord8 for muscle parts
(neck, biceps, forearms, thighs, calves). Stats cards gain a
matching 8%-tint fill and accent-colored hover border. History
page header image enlarged. Thigh SVG stroke-width bumped to 11
for better mask legibility.
Latest measurements render as a 3x3 card grid (vertical mobile,
horizontal on ≥768px) linking to `/fitness/{measure}/{history}/{part}`
with summary stats + chart. Slugs localize (hals, oberschenkel, …)
when on the German route.
Alexander
