Refactor image mesh processing and background removal functionality

- Updated NODE_GROUP_NAME from "O Refine DA3 Surface" to "O DA3 Surface".
- Introduced `remove_surface_background` function to filter out background faces and compact geometry.
- Enhanced `build_image_mesh` to conditionally remove background faces based on a new property.
- Added `snapform_remove_background` and `snapform_keep_original` properties to operators for better control over background handling.
- Updated UI to reflect new properties and improved resolution scaling logic.
- Refactored tests to cover new background removal functionality and ensure proper geometry handling.
- Adjusted geometry nodes and validation scripts to remove references to background handling.

tests/test_worker.py

@@ -1340,6 +1340,20 @@ class WorkerTest(unittest.TestCase):
         )
         np.testing.assert_array_equal(compact_faces, [[0, 1, 2]])
 
+    def test_surface_background_faces_are_removed_before_export(self):
+        faces = np.asarray(
+            ((0, 1, 4), (0, 4, 3), (1, 2, 5), (1, 5, 4)),
+            dtype=np.int32,
+        )
+        foreground = np.asarray(
+            ((False, True, True), (False, True, True)),
+            dtype=bool,
+        )
+
+        filtered = self.worker.remove_background_faces(faces, foreground)
+
+        np.testing.assert_array_equal(filtered, faces[2:])
+
     def test_image_mesh_data_keeps_camera_geometry_and_uv(self):
         class FakeImage:
             def __enter__(self):