The accounts page offers "remove the organization too" behind a confirm page that lists everything that will go

Replaces #1488. Its pulls went red on tests unrelated to the accounts page.

Done looks like

[ ] For an admin, the last_owner refusal in src/web/pages/accounts.ts links to a confirm page for that account.
[ ] The confirm page is server-rendered from the read-only listing. It shows each organization, each repository it owns (and its app), and the teams, every name escaped. Visiting it removes nothing.
[ ] Its same-origin POST calls the existing confirmed retire action. Afterwards the page says what was removed. On a partial failure, it says what was removed and that trying again finishes the job.
[ ] Tests in test/accounts*.test.ts: the listing is complete and escaped, a visit has no side effect, and non-admin and cross-origin requests are refused. Tests that make app tokens stop their environments.

The accounts page offers "remove the organization too" behind a confirm page that lists everything that will go #1626