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.

tools/nodes/arrangement/zones.py

@@ -0,0 +1,28 @@
+"""Identify paired execution zones and their exclusive input calculations."""
+
+from graphlib import TopologicalSorter
+
+
+def node_zones(node_group):
+    """Return each paired entry, exit, and its data-dependent node membership."""
+    parents = {node: set() for node in node_group.nodes}
+    children = {node: set() for node in node_group.nodes}
+    for link in node_group.links:
+        parents[link.to_node].add(link.from_node)
+        children[link.from_node].add(link.to_node)
+    order = list(TopologicalSorter(parents).static_order())
+    ancestors = {}
+    for node in order:
+        ancestors[node] = parents[node] | set().union(*(ancestors[parent] for parent in parents[node]))
+    zones = []
+    for entry in order:
+        end = getattr(entry, "paired_output", None)
+        if end is None:
+            continue
+        members = {node for node in ancestors[end] if entry in ancestors[node]} | {entry, end}
+        for node in reversed(order):
+            if (node not in members and node in ancestors[end] and children[node]
+                    and children[node] <= members and entry not in children[node]):
+                members.add(node)
+        zones.append((entry, end, members))
+    return zones