feat(core,fuse,gui): places on a world map

The Places view gets a Grid/Map toggle. The map shows a bubble per town,
sized by its number of photos, over the outline of the world's land. Towns
whose bubbles would overlap merge into one that counts all their photos, and
clicking it zooms in until they part; clicking a single town opens it like a
card does. Drag to pan, scroll or pinch to zoom, and the buttons zoom in,
zoom out or frame every place again. Hovering names the town, or the first
few towns of a merged bubble.

No tile server is involved: none that is free has terms allowing an app like
this one to use it. The map is drawn from Natural Earth's 1:50m land
polygons (public domain), trimmed and simplified by
scripts/natural-earth-land.py into crates/pdfs-gui/data/land.txt, in Web
Mercator. The About dialog credits Natural Earth.

PlaceInfo carries the town's latitude and longitude; a daemon older than the
map sends none, and its towns are left off the map.

README.md

@@ -75,7 +75,7 @@ pdfs-app            # the desktop app
 - **File Version History**: Every revision Proton Drive still holds for a file, from the browser's details pane (**Versions**) or `pdfs versions list|restore|save|rm`. Restoring is server-side — no re-upload — and an old version can be written out to a local file without touching the live one.
 - **Photo Favourites**: Star a photo in the lightbox, filter the gallery to favourites, or use `pdfs favorite <uid>` / `pdfs photos --favorites`.
 - **Photo Albums**: Browse your albums — including the ones shared with you — from the Albums view of the Photos page, or with `pdfs albums` / `pdfs album <uid>`. Album contents open in the same gallery as the timeline.
-- **Places**: The Places view of the Photos page groups photos by the town they were taken in, using the location stored with each photo. Towns are looked up offline in [GeoNames](https://www.geonames.org/) data (CC BY 4.0); install `iso-codes` for country names in your language.
+- **Places**: The Places view of the Photos page groups photos by the town they were taken in, using the location stored with each photo, as cards or on a world map. Towns are looked up offline in [GeoNames](https://www.geonames.org/) data (CC BY 4.0), and the map is drawn offline from [Natural Earth](https://www.naturalearthdata.com/) land outlines (public domain), so no map tiles are fetched; install `iso-codes` for country names in your language.
 - **Human Verification (CAPTCHA) Recovery**: Detects sign-in gates (VPN/new IP challenges) and launches an embedded `WebKitWebView` dialog to safely complete the challenge, transparently retrying authentication with the earned token.
 - **Selective Sync (`.pdfsignore`)**: Keep build trees, dependency directories, and editor leftovers out of synced folders using gitignore-style rules.
 - **Data-Safe Offline Writes**: Durable scratch/staging files and a transactional pending queue preserve acknowledged writes across network failures and restarts.