Remove unused Timestripe blog covers

src/routes/assets/ contains 137 files, 96 MB in total, all tracked in git. They are cover images from the Timestripe blog: what-is-timestripe.jpg, calendars-with-timestripe-cover.jpg, how_to_use_timestripe_with_firefox_cover.jpg, timestripe-notion-cover.avif, timestripe-team-cover.avif, the whole vs-akiflow / vs-asana / vs-notion / vs-todoist comparison series (with copy duplicates), blackfriday.png, prodlyonka-cover-1.jpg and so on.

A grep of every basename against src finds no import. The only hit, cover.avif, is a string literal in src/lib/url-utils.test.js, not a file import.

Tasks

• Delete src/routes/assets/ entirely, or keep one or two neutral covers that the demo pages actually reference
• Re-run the basename grep after deletion and confirm pnpm build still passes
• Consider whether the .imagetools-cache/ CI cache needs a key bump so it does not keep stale derivatives