feat: migrate omni.isaac.* imports to isaacsim.* via compat layer

- Add core/compat.py: compatibility module with try/except imports
  supporting both IS 4.x (omni.isaac.*) and IS 5.x+ (isaacsim.*)
- Migrate 152 imports across 47 files from direct omni.isaac.* to core.compat
- Handle class renames: RigidPrim→SingleRigidPrim, GeometryPrim→SingleGeometryPrim,
  XFormPrim→SingleXFormPrim, Articulation→SingleArticulation (aliased for compatibility)
- Add migerate/migrate_imports.py: automated migration script for future use
- Leave debug_draw and env_loader try/except imports as-is

This eliminates ~100 deprecation warnings from our code on IS 5.0,
and future-proofs for IS 6.x when old APIs may be removed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

workflows/simbox/core/cameras/custom_camera.py

@@ -2,13 +2,10 @@ import numpy as np
 import omni.replicator.core as rep
 from core.cameras.base_camera import register_camera
 from core.utils.camera_utils import get_src
-from omni.isaac.core.prims import XFormPrim
-from omni.isaac.core.utils.prims import get_prim_at_path
-from omni.isaac.core.utils.transformations import (
-    get_relative_transform,
-    pose_from_tf_matrix,
-)
-from omni.isaac.sensor import Camera
+from core.compat import XFormPrim
+from core.compat import get_prim_at_path
+from core.compat import get_relative_transform, pose_from_tf_matrix
+from core.compat import Camera
 
 
 @register_camera