feat(node_assets): add image plane geometry nodes and validation scripts

- Implemented `image_plane.py` to build the Image Plane Geometry Nodes group with customizable parameters for geometry, subdivide, and thickness.
- Created `image_plane_validation.py` to validate the functionality of the image plane, ensuring correct geometry generation and material assignment.
- Developed `material_layers.py` to construct shader node groups for image materials, including depth and normal handling.
- Authored `plane_layouts.py` to define node arrangements for image geometry assets.
- Introduced `shadeless.py` to create a shadeless shader node group that displays color without scene lighting while preserving shadows and reflections.

tests/server_test_support.py

@@ -0,0 +1,102 @@
+import sys
+from pathlib import Path
+from types import SimpleNamespace
+
+
+PROJECT_ROOT = Path(__file__).resolve().parents[1]
+
+
+def load_server_module(name):
+    addon_directory = PROJECT_ROOT / "src" / "anyimage"
+    sys.path.insert(0, str(addon_directory))
+    try:
+        return __import__(f"server.{name}", fromlist=[name])
+    finally:
+        sys.path.remove(str(addon_directory))
+
+
+def _make_fake_av(frame_count):
+    """Build a fake av module yielding frame_count integer-valued frames."""
+    class FakeImage:
+        def __init__(self, value):
+            self.value = value
+
+        def save(self, path, format=None):
+            Path(path).write_text(str(self.value), encoding="utf-8")
+
+    class FakeFrame:
+        def __init__(self, value):
+            self.value = value
+
+        def to_image(self):
+            return FakeImage(self.value)
+
+    class FakeContainer:
+        def __init__(self):
+            self.position = 0
+            self.closed = False
+            self.streams = SimpleNamespace(video=[object()])
+
+        def decode(self, _stream):
+            while self.position < frame_count:
+                frame = FakeFrame(self.position)
+                self.position += 1
+                yield frame
+
+        def close(self):
+            self.closed = True
+
+    class FakeAv:
+        def __init__(self):
+            self.containers = []
+
+        def open(self, _path):
+            container = FakeContainer()
+            self.containers.append(container)
+            return container
+
+    return FakeAv()
+
+
+class FakeModels:
+    def __init__(self, directory="model"):
+        self.model_directory = Path(directory)
+
+    def directory(self, _model):
+        return self.model_directory
+
+    def get_ben2(self, _model_directory, _device):
+        from server.models.onnx_ben2 import create_session
+
+        return create_session(self.model_directory, "cpu"), 0.0
+
+
+    def get_upscale(self, _model_directory, _device):
+        return object()
+
+
+class FakeJobContext:
+    def __init__(self, directory, job_type, models=None):
+        self.directory = Path(directory)
+        self.job_type = job_type
+        self.models = models or FakeModels()
+        self.status = {}
+        self.logs = []
+
+    def resource(self, name):
+        if name != "model_manager":
+            raise KeyError(name)
+        return self.models
+
+    def progress(self, progress, message, **details):
+        self.status = {
+            "progress": progress,
+            "message": message,
+            **details,
+        }
+
+    def log(self, message, *, level="INFO"):
+        self.logs.append((level, message))
+
+    def check_cancelled(self):
+        return None