Show local spots in bold and name the computer that made them

A spot an operator put on a bandmap, here or on another computer, is
drawn in bold. Its hover text names the computer instead of the
spotter's callsign. A spot from another computer carries the name from
the ADDSPOT message.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Nonemm.Spotting/Spot.cs

@@ -35,6 +35,14 @@ public sealed record Spot(
             IsStation = false,
         };
 
+    /// The computer on the network that put the spot on the bandmap, or empty
+    /// for a spot that came from the cluster.
+    public string Computer { get; init; } = "";
+
+    /// A spot an operator put on a bandmap, here or on another computer, as
+    /// opposed to one from the cluster.
+    public bool IsLocal => Source == SpotSource.Operator && IsStation;
+
     public bool IsSplit => Qsx.Hertz > 0;
 
     public Band? Band => Bands.ForFrequency(Frequency);