Compute nearby-brewery distance in SQL instead of client-side Haversine, and add the spatial index it relies on.

web/backend/Features/Features.Breweries/Dtos/BreweryDto.cs

@@ -32,8 +32,13 @@ public record BreweryDto(
     byte[]? RowVersion,
     BreweryLocationDto? Location
 );
+/// <param name="DistanceMetres">
+///     The distance, in metres, from a query's origin point, or <see langword="null"/> for queries with no
+///     origin point (e.g. <c>GET /api/brewery/locations</c>).
+/// </param>
 public record SimplifiedBreweryDto(
     Guid BreweryPostId,
     string BreweryName,
-    BreweryLocationDto? Location
+    BreweryLocationDto? Location,
+    double? DistanceMetres
 );

web/backend/Features/Features.Breweries/Dtos/BreweryDtoMapper.cs

@@ -68,7 +68,8 @@ public static class BreweryDtoMapper
                     AddressLine2: brewery.Location.AddressLine2,
                     PostalCode: brewery.Location.PostalCode,
                     Coordinates: brewery.Location.Coordinates
-                )
+                ),
+            DistanceMetres: brewery.Distance?.DistanceMetres
         );
     }
 }