feat: Add new Geometry Nodes groups for image relief and shadeless shader

- Implemented the "O Image Relief Plane" Geometry Nodes group to create a fixed-base image relief using depth images and various parameters.
- Created the "O Shadeless" shader node group to display color without scene lighting while preserving shadows and reflections.
- Introduced a preview feature for node groups, allowing for interactive visualization of node arrangements in an HTML format.
- Added a template HTML file for rendering node previews with customizable views and controls.

tests/test_cutout_objects.py

@@ -123,7 +123,8 @@ def test_depth_result_image_loads_server_vector_exr_and_keeps_data_name(tmp_path
         points=points,
     )
     path = tmp_path / "depth.exr"
-    write_depth_texture(frame, path)
+    alpha = np.asarray(((0.8, 1.0), (0.75, 0.0)), dtype=np.float32)
+    write_depth_texture(frame, path, alpha=alpha)
     metadata = _depth_metadata(np.eye(3), (2, 2), 1.0)
 
     image = depth_data.load_depth_result_image(path, source, metadata)
@@ -132,7 +133,10 @@ def test_depth_result_image_loads_server_vector_exr_and_keeps_data_name(tmp_path
     image.pixels.foreach_get(packed)
     packed = np.flipud(packed.reshape((2, 2, 4)))
     assert np.array_equal(packed[..., :3], points)
-    assert np.array_equal(packed[..., 3], validity)
+    assert np.array_equal(packed[..., 3], alpha * validity)
+    camera_depth, valid = depth_data.camera_depth_values(image)
+    np.testing.assert_array_equal(camera_depth, points[..., 2])
+    np.testing.assert_array_equal(valid, alpha * validity > 0.5)
     assert image.alpha_mode == "CHANNEL_PACKED"
     assert image.name == "Source_depth.exr"
 
@@ -149,7 +153,7 @@ def test_depth_texture_keeps_points_outside_positive_validity(tmp_path):
         intrinsics=np.eye(3, dtype=np.float32),
     )
     path = tmp_path / "depth.exr"
-    write_depth_texture(frame, path)
+    write_depth_texture(frame, path, alpha=np.ones_like(frame.validity))
 
     image = depth_data.load_depth_result_image(
         path,