docs: screenshots that regenerate themselves, and eleven of them

They were many rounds behind — no settings, no task detail, no themes, no groups,
no colours, no calendar, no admin pages. The reason is in how they were made:
`tools/shots` needs a running instance and a session cookie pasted in by hand, so
it ran about as often as somebody felt like doing that.

`node scripts/generate-screenshots.js` starts the real binary, creates its own
account, fills it with Danish demo data and photographs eleven surfaces into both
`site/screenshots` and `docs/screenshots`. Nothing to set up and nothing to
remember.

A script rather than a test, for the same reason `generate-icons.js` is one: CI
must never rewrite a tracked binary file.

`tools/shots` stays. It is still the way to photograph an instance that is
already running rather than a fresh one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -118,8 +118,15 @@ accented `o` and a Danish-first app that cannot do this is broken for its own us
 |---|---|
 | ![Board view](site/screenshots/board.png) | ![Light theme](site/screenshots/today-light.png) |
 | Board view — one column per section. | The light theme. |
+| ![A week on Upcoming](site/screenshots/week.png) | ![A task, opened](site/screenshots/detail.png) |
+| A week at a time, so a task can be dragged across a month boundary. | A task, opened. |
+| ![The five themes](site/screenshots/themes.png) | ![Instance history](site/screenshots/history.png) |
+| Five themes, all measured for contrast. | What has been done on the server. |
 
-Regenerate these with `go run ./tools/shots` against a running instance.
+Regenerate these with `node scripts/generate-screenshots.js` from `web/`. It starts
+the real binary, creates its own account, fills it with demo data and photographs
+eleven surfaces — nothing to set up and nothing to remember. (`go run ./tools/shots`
+still works, and is the way to photograph an instance that is already running.)
 
 ## Running it