Add operators for model downloading and surface generation

- Implemented `DownloadModel` and `DownloadRequiredModels` operators for downloading models.
- Created `ClearModels` operator to clear model resources.
- Added `ConvertToSurface` operator for converting image empties into textured surfaces.
- Introduced `GenerateDa3Surface` and `GenerateMoge2Surface` operators for generating surfaces using DA3 and MoGe-2 models respectively.
- Developed utility functions for handling image mesh data, assigning attributes, and managing geometry nodes.
- Established runtime configuration and post-installation model downloading in `runtime.py`.

src/snapform/operators/__init__.py

@@ -0,0 +1,34 @@
+from .background import ProcessImageBackground, RemoveImageBackground
+from .balloon import BalloonLasso, ExtractBalloon
+from .debug import DebugBen2, DebugDa3, DebugMoge2
+from .depth_plane import (
+    ConvertToDepthPlane,
+    ExtractOriginalFrames,
+    GenerateDa3Depth,
+    GenerateMoge2Depth,
+    GenerateOriginalBackground,
+)
+from .models import ClearModels, DownloadModel, DownloadRequiredModels
+from .surface import ConvertToSurface, GenerateDa3Surface, GenerateMoge2Surface
+
+
+CLASSES = (
+    DownloadModel,
+    DownloadRequiredModels,
+    DebugDa3,
+    DebugMoge2,
+    DebugBen2,
+    GenerateDa3Depth,
+    GenerateMoge2Depth,
+    GenerateDa3Surface,
+    GenerateMoge2Surface,
+    ProcessImageBackground,
+    GenerateOriginalBackground,
+    ExtractOriginalFrames,
+    ClearModels,
+    ExtractBalloon,
+    BalloonLasso,
+    RemoveImageBackground,
+    ConvertToDepthPlane,
+    ConvertToSurface,
+)