feat: Add multiplayer networking architecture and documentation updates

- Updated Master Blueprint Index to include Multiplayer Networking support.
- Added detailed Multiplayer Networking sections across all developer documentation (01-11).
- Introduced authority maps, key patterns, and RPC guidelines for each system.
- Established a comprehensive multiplayer networking architecture document outlining core principles, replication strategies, and anti-cheat considerations.
- Enhanced UI documentation to clarify local-only behavior and binding to replicated dispatchers.
- Implemented client prediction strategies and RPC naming conventions for consistency across the framework.

docs/blueprints/02-player/13_BPC_EmbodimentSystem.md

@@ -255,4 +255,21 @@ flowchart TD
 
 ---
 
+## 11. Multiplayer Networking
+
+**Replication: Minimal.** Embodiment is primarily local rendering. Only visibility mode and overlay state sync for shared visual consistency.
+
+| Variable | Condition | Purpose |
+|----------|-----------|---------|
+| `CurrentVisibility` | `Replicated` | Other clients see correct body visibility (FullBody in mirrors/death) |
+| `CurrentOverlay` | `Replicated` | Blood/water visible to other players |
+| Arms IK, wall proximity, overlay blending | **Local only** | First-person rendering is per-client |
+
+### Authority
+- `SetVisibilityMode` is server-authoritative for replicated variable; client applies local mesh changes.
+- `ApplyOverlay` and `ClearOverlay` are server-authoritative.
+- `CheckWallProximity` and `ApplyOverlayBlendTick` are **local only**.
+
+---
+
 *Blueprint Spec: Embodiment System. Conforms to TEMPLATE.md v1.0 — part of the UE5 Modular Game Framework.*