Regenerate the install/notification icons from tchatou.fr's own favicon
(France-blue tile + speech bubbles). Bump the SW cache version so clients
fetch the new icons; push handler unchanged.
iOS only delivers Web Push to a Home-Screen PWA and ignores SVG
apple-touch-icons, and Android can't use SVG notification icons — so the
SVG-only icons broke push on mobile while desktop worked. Add 180/192/512
PNG icons (rendered from the orbit mark) and point the manifest +
apple-touch-icon at them. Push delivery code untouched.
