- users.theme and users.theme_mode, added by migrate(); GET /api/me returns them
and PATCH /api/me saves them, refusing anything but a plain name and
light/dark/auto, since index() writes them into the page's <html> tag.
- The page arrives with data-theme and data-choice already on <html> (and
data-mode unless Auto), so it is drawn in the account's theme from the start.
- A theme a browser kept in localStorage goes up to the account once, the first
time an account with none loads the page.
- Saves go one at a time, each with the choice as it stands: sent all at once, a
quick run through the list could land out of order and keep a theme passed on
the way. The browser test caught it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>