Refactor depth reference handling and cleanup

- Unified reference depth calculation to use a single implementation in common/depth.py.
- Removed server-side reference depth computation and adjusted depth.json to only include image_size and intrinsics.
- Updated depth texture handling to ignore transparent, invalid, and non-positive pixels when calculating reference depth.
- Changed reference depth calculation to use the 95th percentile of valid depth values.
- Adjusted depth direction fitting to return a flat direction when no samples are available.
- Removed cleanup threshold parameters from Cutout and related nodes, simplifying the interface.
- Updated tests to verify new reference depth logic and ensure compatibility with existing functionality.

tests/anyimage/server/test_model_geometry.py

@@ -30,7 +30,7 @@ def test_moge_infer_returns_geometry_frame_with_model_validity():
     )
 
 
-def test_moge_z_depth_frame_does_not_require_points():
+def test_moge_frame_omits_points_when_not_requested():
     prediction = {
         "depth": np.ones((2, 2), dtype=np.float32),
         "normal": np.zeros((2, 2, 3), dtype=np.float32),