Fix devcontainer .NET version mismatch - update to support .NET 9.0

Co-authored-by: TheAngryByrd <[email protected]>

Author: Copilot

.devcontainer/devcontainer.json

@@ -23,7 +23,8 @@
         "ghcr.io/devcontainers-contrib/features/starship:1": {},
         // https://github.com/devcontainers/features/blob/main/src/dotnet/README.md
         "ghcr.io/devcontainers/features/dotnet:2": {
-            "version": "8.0"
+            "version": "9.0",
+            "additionalVersions": "8.0"
         }
     },
     "overrideFeatureInstallOrder": [