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/build_geometry_nodes_asset.py

@@ -708,7 +708,7 @@ def build_depth_plane_group():
         "INPUT",
         "NodeSocketFloat",
     )
-    background_depth.default_value = 0.0
+    background_depth.default_value = -1.0
     background_depth.min_value = -10000.0
     background_depth.max_value = 10000.0
     background_depth.subtype = "DISTANCE"