Administer the directory from iPX with an rwa token (#206)

A Directory feed's page offers Check now and Remove to an admin whose token is rwa (the page
learns it from can_admin on the feed's page, asked of the directory only for admins). Admin,
Directory lists the servers sharing, from a new GET /v1/instances, and the blocked feeds by
title: a feed is often blocked because its address carries a key, so the address stays in the
directory. Unblocking or dropping a snapshot sends this server's snapshot again at once; since
directory's 403 reaches the page as 403, not 502.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture.md

@@ -161,6 +161,8 @@ else a `401`. A feed's items and files (its entries, `download-latest`, `/api/en
 | `GET /api/opml`, `POST /api/opml` | export your subscriptions; subscribe to every feed in an OPML |
 | `GET /api/directory/{id}` | a feed's page from the directory service (#205), by the directory's id: its description and latest twenty items, sanitized here, and why its last check failed, in words; never a file or its address |
 | `GET /api/popular`, `GET /api/directory`, `POST /api/popular/{id}` | the directory service's ten most subscribed and every feed it lists, A to Z, asked by ipx with its token (directory id, title, art, subscribers across every sharing server, whether it is yours and its id here, category, whether it carries audio or video; never a URL); subscribe by the directory's id, which takes the feed's address from the directory. `503` with no directory set up |
+| `DELETE /api/directory/{id}`, `POST /api/directory/{id}/refresh` | admin-only, and the directory refuses unless this server's token is `rwa` (#206): remove and block a feed; check it now. `GET /api/directory/{id}` says `can_admin` when both hold |
+| `GET /api/directory-admin`, `DELETE /api/directory-blocked/{id}`, `DELETE /api/directory-instances/{name}` | admin-only, `rwa` (#206): the servers sharing (name, feeds, subscribers) and the blocked feeds (id, title, when; never the address, often why it was blocked); unblock; drop a server's snapshot. Unblocking or dropping sends this server's snapshot again at once |
 | `GET /api/directory-status` | admin-only: the name and access the directory gives this server's token, or why it refused, and how the last snapshot went |
 | `GET /api/settings`, `PATCH /api/settings` | admin-only to write. The directory's token is written, never read back: `directory_token_set` says whether there is one |
 | `GET /api/users`, `POST /api/users`, `PATCH /api/users/{id}`, `DELETE /api/users/{id}` | admin-only; the only admin cannot be demoted or removed |