feat: add UE5 LED display client — backend API, C++ source, stereo framework

Backend:
- Add /api/v1/ue/* endpoints (compute-points, cables, landing-points, satellites, status)
  returning flat JSON optimised for UE5 C++ parsing

UE5 client (ue_client/):
- PlanetDataManager: HTTP fetch + local mock JSON loader, spawns ComputePointActors
- ComputePointActor / InteractiveObjectBase: hover/select state, material switching
- GlobeInteractionComponent: drag-to-rotate via CesiumGeoreference origin shift, inertia, zoom
- StereoRenderingManager: runtime SbS/TbB stereo toggle, IPD control (format TBD)
- MotionCaptureInterface: protocol-agnostic gesture/rotate/zoom delegate interface (impl TBD)
- PlanetPlayerController: unified mouse + motion-capture input routing
- PlanetGameMode, Build.cs, Config, mock data

Docs:
- ue5_mvp_fused_plan.md updated to v3.0 for LED display context
- ue_client_setup_guide.md: step-by-step editor setup guide
- ue_todo.md: pending items blocked on vendor answers (stereo format + mocap protocol)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ue_client/Source/PlanetClient/PlanetClient.Build.cs

@@ -0,0 +1,33 @@
+using UnrealBuildTool;
+
+public class PlanetClient : ModuleRules
+{
+    public PlanetClient(ReadOnlyTargetRules Target) : base(Target)
+    {
+        PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;
+
+        PublicDependencyModuleNames.AddRange(new string[]
+        {
+            "Core",
+            "CoreUObject",
+            "Engine",
+            "InputCore",
+            "HTTP",
+            "Json",
+            "JsonUtilities",
+            "CesiumRuntime",
+            "UMG",
+            "Slate",
+            "SlateCore",
+            "RenderCore",        // StereoRenderingManager 用到
+            "RHI",               // 渲染硬件接口
+            // TODO: 动捕协议确认后按需添加：
+            // "LiveLink",         // Live Link 协议
+            // "LiveLinkInterface",
+            // "Networking",       // OSC/UDP 协议
+            // "Sockets",
+        });
+
+        PrivateDependencyModuleNames.AddRange(new string[] { });
+    }
+}