Initial project scaffold for VS Vineyard mod

Sets up C# .NET 8 project with modinfo.json, ModSystem entry point,
full asset directory structure, .gitignore, and README.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,19 @@
+# Build output
+bin/
+obj/
+releases/
+
+# IDE
+.vs/
+.vscode/
+*.user
+*.suo
+.idea/
+*.iml
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Logs
+*.log