Closes#796.
The maps API has accepted and persisted `notes` on map markers since
PR #770, but the marker popup component still rendered name only and
ignored the field. Now the popup shows a notes block beneath the name
when it's populated, with whitespace preserved and long text wrapped.
Threaded `notes` through the read path:
- `api.listMapMarkers` / `api.createMapMarker` response types
- `MapMarker` interface in `useMapMarkers` and the data.map projection
- `MapComponent`'s selectedMarker popup
The create/update UI is unchanged — users still set notes via the API
or DB directly, matching the issue's stated scope. A marker entry with
empty/whitespace-only notes renders the same as before.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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