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

web/backend/Domain/Domain.Entities/Entities/BreweryPost.cs

@@ -21,4 +21,7 @@ public sealed class BreweryPost
     // Navigation Properties
     public BreweryPostLocation? Location { get; set; }
     public List<BeerPost> BeerPosts { get; set; } = [];
+
+    // Query-computed
+    public DistanceInformation? Distance { get; set; }
 }

web/backend/Domain/Domain.Entities/Entities/BreweryPostLocation.cs

@@ -2,6 +2,8 @@ namespace Domain.Entities;
 
 public sealed record CoordinateData(double Latitude, double Longitude);
 
+/// <summary>The distance, as computed by the database, from a query's origin point to a brewery.</summary>
+public sealed record DistanceInformation(CoordinateData From, double DistanceMetres);
 
 public sealed class BreweryPostLocation
 {