Stops older dumps from showing a site's icon as their thumbnail. The metadata
fetch used to fall back on the page's icon, and then on a guessed
/favicon.ico, so most thumbnails were a 16×16 icon, or a 404, that the UI
stretched over a 128×72 box. It now stops at real artwork, and a missing
thumbnailUrl means none, which the frontend draws a placeholder for. This
gives the older rows that meaning, by moving their icons out of
rich_content.thumbnailUrl into the new faviconUrl.
It judges the stored URL alone and fetches nothing, so it doesn't fill
accentColor. The frontend derives a hue from the hostname when it is
missing, and refreshing a dump's metadata fetches the real one.
Run once by runMigrations. It leaves alone a row that already has a
faviconUrl, and one whose rich_content doesn't parse. 0012 undoes its
mistakes.
Usage
import * as mod from "api/db/migrations/0011_split_favicon_thumbnail.ts";