feat: visual refresh — lighter typography, message animations, richer themes
Typography: body text W400→W300 for airier feel, headings scaled up
(H1 26sp, H2 22sp, H3 18sp), W600/W500 weight hierarchy for contrast.
Animations: animateItem() on LazyColumn messages — 350ms fade-in,
spring placement, 200ms fade-out.
Themes: blobs 20% larger + better full-screen distribution, higher
alpha on OLED (0.48 peak), light mode factor 0.65→0.78, reduced
vignette, distinct primaryDeep per theme for richer gradients.
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