fix(images): full-width timeline media at 1280px (was 640, blurry on mobile retina)
The News-feed media is full-width — on a phone that's ~430px CSS x 3 DPR ~= 1290 physical px,
so the 640px thumbnail was upscaled and looked low-quality. Serve it at 1280px (crisp on
mobile/desktop retina; capped at the original width). Grid/list covers stay small (their
display is small; a bigger thumb would over-downscale line-art on desktop).
- services/ThumbnailService.js — add 1280 to the size whitelist
- views/pages/news.ejs — feed media thumb 640 -> 1280