ue5.7: add architecture diagrams to README, set EngineVersion 5.7.0

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

README.md

@@ -3,7 +3,24 @@
 Universal, server-authoritative, data-driven framework for items, inventory,
 interaction, carrying, equipment, world-slot installation, placement and item
 features. Built for co-op horror / survival / extraction / puzzle projects.
-Tested compiling against **Unreal Engine 5.7**.
+Tested compiling against **Unreal Engine 5.7** (`ue5.7` branch) and **5.8** (`ue5.8` branch).
+
+## Architecture at a glance
+
+![Item Interaction Ecosystem — system architecture](Docs/images/all-systems.png)
+
+<details>
+<summary>More diagrams (interaction flow, inventory system)</summary>
+
+**Interaction flow — client → server → replication**
+
+![Interaction flow](Docs/images/interaction-flow.png)
+
+**Inventory system — containers, slots, operations, replication**
+
+![Inventory system](Docs/images/3.png)
+
+</details>
 
 > Status: all C++ runtime + editor modules implemented and compiling (spec stages
 > 1–11). Binary content (UMG widgets, the test map, and the DataTable *assets*