Refactor AI Host to Backend Service and update related components

- Renamed references from "AI Host" to "Backend Service" throughout the codebase for consistency.
- Updated the registration and unregistration of context menus to include the Outliner.
- Changed the job protocol versioning and related constants for clarity.
- Modified the runtime installation messages and error handling to reflect the new terminology.
- Adjusted the user interface labels and messages in panels and operators to align with the new Backend Service terminology.
- Updated tests to ensure they reflect the changes in naming and functionality.
- Changed default value for background depth in geometry nodes asset to -1.0 for better handling of depth planes.

tools/validate_depth_plane_asset.py

@@ -29,6 +29,7 @@ def main():
     )
     assert background_depth.subtype == "DISTANCE"
     assert background_depth.structure_type == "SINGLE"
+    assert background_depth.default_value == -1.0
     frame_input = next(
         item
         for item in group.interface.items_tree