Initial commit: Complete open-source Decal rebuild

All 5 phases of the open-source Decal rebuild:

Phase 1: 14 decompiled .NET projects (Interop.*, Adapter, FileService, DecalUtil)
Phase 2: 10 native DLLs rewritten as C# COM servers with matching GUIDs
  - DecalDat, DHS, SpellFilter, DecalInput, DecalNet, DecalFilters
  - Decal.Core, DecalControls, DecalRender, D3DService
Phase 3: C++ shims for Inject.DLL (D3D9 hooking) and LauncherHook.DLL
Phase 4: DenAgent WinForms tray application
Phase 5: WiX installer and build script

25 C# projects building with 0 errors.
Native C++ projects require VS 2022 + Windows SDK (x86).

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

Native/DecalSupportLibraries/Attic/DecalSupportLibraries.h

@@ -0,0 +1,31 @@
+// DecalSupportLibraries.h : main header file for the PROJECT_NAME application
+//
+
+#pragma once
+
+#ifndef __AFXWIN_H__
+	#error include 'stdafx.h' before including this file for PCH
+#endif
+
+#include "resource.h"		// main symbols
+
+
+// CDecalSupportLibrariesApp:
+// See DecalSupportLibraries.cpp for the implementation of this class
+//
+
+class CDecalSupportLibrariesApp : public CWinApp
+{
+public:
+	CDecalSupportLibrariesApp();
+
+// Overrides
+	public:
+	virtual BOOL InitInstance();
+
+// Implementation
+
+	DECLARE_MESSAGE_MAP()
+};
+
+extern CDecalSupportLibrariesApp theApp;