fix: conv2d bias (#12834)

ml/nn/convolution.go

@@ -10,7 +10,8 @@ type Conv2D struct {
 func (m *Conv2D) Forward(ctx ml.Context, t ml.Tensor, s0, s1, p0, p1, d0, d1 int) ml.Tensor {
 	t = m.Weight.Conv2D(ctx, t, s0, s1, p0, p1, d0, d1)
 	if m.Bias != nil {
-		t = t.Add(ctx, m.Bias)
+		// Bias shape is (out_channels,) while t shape is (width, height, out_channels, batch)
+		t = t.Add(ctx, m.Bias.Reshape(ctx, 1, 1, -1))
 	}
 	return t
 }