Initialize dotnet-version-upgrade scenario

.github/upgrades/scenarios/dotnet-version-upgrade/scenario-instructions.md

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+# .NET Version Upgrade
+
+## Preferences
+- **Flow Mode**: Automatic
+- **Target Framework**: net10.0
+
+## Source Control
+- **Source Branch**: develop
+- **Working Branch**: upgrade-dotnet-10
+- **Commit Strategy**: After Each Task
+- **Branch Sync**: Auto (Merge)