feat: add programmatic tray icon generation (green/yellow/red)

src/SpamGuard/Tray/IconGenerator.cs

@@ -0,0 +1,28 @@
+namespace SpamGuard.Tray;
+
+using System.Drawing;
+using System.Drawing.Drawing2D;
+
+public static class IconGenerator
+{
+    public static Icon CreateCircleIcon(Color color, int size = 16)
+    {
+        using var bitmap = new Bitmap(size, size);
+        using var graphics = Graphics.FromImage(bitmap);
+        graphics.SmoothingMode = SmoothingMode.AntiAlias;
+        graphics.Clear(Color.Transparent);
+
+        using var brush = new SolidBrush(color);
+        graphics.FillEllipse(brush, 1, 1, size - 2, size - 2);
+
+        // Add a subtle border
+        using var pen = new Pen(Color.FromArgb(100, 0, 0, 0), 1);
+        graphics.DrawEllipse(pen, 1, 1, size - 3, size - 3);
+
+        return Icon.FromHandle(bitmap.GetHicon());
+    }
+
+    public static Icon Green => CreateCircleIcon(Color.FromArgb(76, 175, 80));
+    public static Icon Yellow => CreateCircleIcon(Color.FromArgb(255, 193, 7));
+    public static Icon Red => CreateCircleIcon(Color.FromArgb(244, 67, 54));
+}