Add Planar Capture System implementation checklist and developer reference

- Created a comprehensive implementation checklist for the Planar Capture System (Systems 136-147) detailing tasks across multiple phases including C++ core, material foundation, Blueprint actors, data assets, integration, and performance testing.
- Added a developer reference document outlining the architecture, data flow, state machine, budget enforcement, render target pooling, horror features, integration points, multiplayer networking, performance characteristics, debugging methods, and build order for the capture systems.
- Introduced examples of capture surface usage in the Project Void horror game, including specific implementations for mirrors, monitors, portals, and fake windows, along with a checklist for integration tasks.

Source/PG_Framework/Private/Capture/PlanarCaptureCommon.cpp

@@ -0,0 +1,6 @@
+// Copyright Ngonart OU. All Rights Reserved.
+// UE5 Modular Game Framework — PlanarCaptureCommon implementation (trivial)
+
+#include "Capture/PlanarCaptureCommon.h"
+// Struct and enum definitions are header-only.
+// This file exists for module compilation unity.