feat(places): descriptions from the place's own website

Overture has no descriptions, and the encyclopaedias only describe the
places that have an article, which is a fraction of a percent. What
Overture does have is the address of the page the description is on, for
43 percent of places, and those pages publish a summary in JSON-LD or
og:description precisely so machines can read it.

The API fetches each page once and keeps the summary; every instance
reads it from there. TREK never opens a business's website itself, which
would mean one request per instance per place against small servers.

In the ladder it sits below the encyclopaedias and above Google: an
article about this exact place beats the operator's own copy, but for a
restaurant or a shop the operator's summary is the only one that exists.
Credited by host and linked back, with no licence claimed.

shared/src/maps/maps.schema.ts

@@ -131,7 +131,14 @@ export const placePhotoCandidateSchema = z.object({
 });
 export type PlacePhotoCandidate = z.infer<typeof placePhotoCandidateSchema>;
 
-export const placeDescriptionSourceSchema = z.enum(['google', 'osm', 'wikivoyage', 'wikipedia']);
+export const placeDescriptionSourceSchema = z.enum([
+  'google',
+  'osm',
+  'wikivoyage',
+  'wikipedia',
+  /** Quoted from the place's own site, via the TREK Places API. */
+  'website',
+]);
 export type PlaceDescriptionSource = z.infer<typeof placeDescriptionSourceSchema>;
 
 export const placeDescriptionSchema = z.object({