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/03-interaction/16_BPC_InteractionDetector.md

@@ -379,4 +379,29 @@ flowchart TD
 
 ---
 
+## 11. Multiplayer Networking (Expanded)
+
+### Replication
+| Variable | Condition | Purpose |
+|----------|-----------|---------|
+| `CurrentTarget` | `Replicated` | Synced target for UI (other players see what you're looking at) |
+
+### Server RPCs
+| RPC | Direction | Description |
+|-----|-----------|-------------|
+| `Server_PerformInteraction` | Client→Server | Client requests interaction. Server validates range, conditions, then calls I_Interactable. |
+
+### Authority
+- **Detection** (trace, sorting, target selection): runs locally per client.
+- **Interaction execution**: server-authoritative. Client calls `Server_PerformInteraction`; server validates and executes.
+- `ForceSetTarget`: server-only for scripted interactions.
+- `HighlightTarget`: local cosmetic effect per client.
+
+### Client Prediction
+- Interaction prompt: shown immediately based on local trace.
+- Hold progress: shown locally; server confirms completion.
+- Blocked feedback: shown locally if conditions fail client-side; server may also reject.
+
+---
+
 *Blueprint Spec: Interaction Detector. Conforms to TEMPLATE.md v1.0 — part of the UE5 Modular Game Framework.*