Fix OwnYourSwarm checkin parsing to read from properties.checkin

Real OwnYourSwarm requests send the checkin h-card inside
properties.checkin (as an array), not at the top level. The code
was reading from the top-level key so no Place was ever created,
leaving checkin notes blank.

Update tests to match the real request format.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Services/Micropub/Data/EntryData.php

@@ -46,7 +46,7 @@ class EntryData extends MicropubData
                 name: Arr::get($data, 'properties.name.0'),
                 description: Arr::get($data, 'properties.description.0'),
                 geo: Arr::get($data, 'properties.geo.0'),
-                checkin: Arr::get($data, 'checkin'),
+                checkin: Arr::get($data, 'properties.checkin.0'),
                 syndication: Arr::get($data, 'properties.syndication.0'),
                 photos: Arr::get($data, 'properties.photo'),
             );