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.

src/snapform/blender_manifest.toml

@@ -12,7 +12,7 @@ platforms = ["windows-x64", "macos-arm64", "linux-x64"]
 license = ["SPDX:GPL-3.0-or-later"]
 
 [permissions]
-network = "Access the local AI Host and download runtime dependencies and model weights"
+network = "Access the local Backend Service and download environment dependencies and model weights"
 files = "Read source images and store runtime data"
 
 [build]