feat(wm): GPS watermark color + place-name/time toggles, "commune, city" locality

src/utils/locationUtils.ts

@@ -49,12 +49,17 @@ export async function getCurrentGPS(): Promise<GPSInfo | null> {
   }
 }
 
-// The one place-name picker: city first, because "the place" on a stamp means
-// the town people would name, while subregion is Android's subAdminArea — the
-// county/district, i.e. the wrong name for the same coordinates. Shared so the
-// camera stamp and a photo's stamp can never disagree.
+// The one place-name picker, shared so the camera stamp and a photo's stamp can
+// never disagree. A Vietnamese geocoder answers with the commune/ward in
+// subregion (post-2025 two-level administration: the commune is the district-
+// level name) and the province/city in region, while city and district come
+// back null, so the stamp reads "COMMUNE, CITY" instead of a bare city.
 export function localityName(address: Location.LocationGeocodedAddress): string | null {
-  const name = address.city || address.subregion || address.district || address.region;
+  const district = address.subregion || address.district;
+  const city = address.city || address.region;
+  // Same name in both slots (one field echoed twice) must not print twice.
+  const parts = district && district !== city ? [district, city] : [district || city];
+  const name = parts.filter(Boolean).join(', ');
   return name ? name.toUpperCase() : null;
 }