Zoom the text of the log, check, available and bandmap windows

Ctrl+wheel and Ctrl+plus / Ctrl+minus change the text size of the
window in front, and Ctrl+0 puts it back. Each size is kept in the
settings file.

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

src/Nonemm.App/Windows/LogWindow.axaml.cs

@@ -1,3 +1,4 @@
+using Nonemm.App.Configuration;
 using System.Collections.ObjectModel;
 using Avalonia;
 using Avalonia.Collections;
@@ -63,9 +64,27 @@ public sealed partial class LogWindow : RefreshableWindow
         };
         Colour(Rows);
         Colour(Earlier);
+        ApplyFontSize();
+        _ = new FontZoom(this, new Settings().LogFontSize, () => session.Settings.LogFontSize, size =>
+        {
+            session.Save(session.Settings with { LogFontSize = size });
+            ApplyFontSize();
+            builtFor = "";
+            Refresh();
+        });
         Refresh();
     }
 
+    /// The cells take their size from the `LogFontSize` resource, and the
+    /// grids need it too because the column widths are measured from it.
+    private void ApplyFontSize()
+    {
+        double size = session.Settings.LogFontSize;
+        Resources["LogFontSize"] = size;
+        Rows.FontSize = size;
+        Earlier.FontSize = size;
+    }
+
     /// What the operator picked. The grid raises this for the picks this window
     /// makes as well, and those are already known.
     private void RememberPicked(object? sender, SelectionChangedEventArgs e)