Pixelfed places: a remote post's own place, shown and never federated again

A Note's `location` that is a Place with coordinates (Pixelfed sends
them as strings) is kept in the new Post.Place and shown as
Status.privapub.place {name, latitude, longitude, country}; an edit
replaces it. An Event's location stays its own `places`, and nothing
renders a place back out. Closes the INTEROP P2 Pixelfed location gap
and the ROADMAP long-tail item.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

CLAUDE.md

@@ -240,7 +240,8 @@ group www-data and reaches the private mongod; `sudo -u www-data` works too.
    because clients show quotes from it, so everything a 4.3+ client calls because of it must answer: grouped
    notifications (`/api/v2/notifications`, its unread count, groups, accounts and dismiss) and the notification policy.
 7. **What a Mastodon `Status` cannot say goes in `Status.privapub`** (`PrivaPubStatus`): object type, title, excerpt,
-   cover, the author's source, link, video, audio and event details, and up/down votes. Every media URL in it goes
+   cover, the author's source, link, video, audio and event details, a remote post's own place (Pixelfed's `location`,
+   never federated again), and up/down votes. Every media URL in it goes
    through the proxy; only page links (`link.url`, an event's online link) point at the remote site, because following
    one is the reader's choice.