Initial commit: Item Interaction Ecosystem plugin (UE5.7)

Server-authoritative, data-driven item/inventory/interaction/carry/equipment/
world-slot/placement/crafting framework. 8 modules, compiles against UE 5.7.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,18 @@
+# Unreal Engine plugin build artifacts
+Binaries/
+Intermediate/
+Saved/
+DerivedDataCache/
+
+# IDE / OS
+.vs/
+*.VC.db
+*.opensdf
+*.sdf
+*.sln
+*.suo
+*.user
+.idea/
+*.pdb
+Thumbs.db
+.DS_Store