Per W3C spec, purpose: "monochrome" icons use only the alpha channel
as the silhouette; RGB is ignored and replaced with the platform
theme color. The previous monochrome-icon.png was a black-on-white
RGB image with no alpha, so Safari (macOS PWAs) and Chrome (Android
themed icons) treated every pixel as opaque and painted the whole
1024x1024 canvas with theme_color (#ffa4c0) - a solid pink tile.
Regenerate as RGBA with the silhouette in alpha (derived from the
favicon's alpha channel via a sharp-based helper script). Rename to
monochromeicon.png to bust Safari's stuck PWA icon cache from prior
broken installs.
Dark theme was set to "dim" in theme.config.ts while app.css registered
"sunset" as the prefersdark theme. The script's regex required a trailing
comma that didn't exist on the last property, causing silent failures.
