refactor: reorganize Resources module into Core/Asset, Core/IO and Resources subdirectories

- Split core resource architecture into Core/Asset/ (IResource, ResourceManager, ResourceCache, etc.)
- Moved IO layer into Core/IO/ (IResourceLoader, ResourceFileSystem, etc.)
- Reorganized concrete resource types into Resources/{Texture,Mesh,Material,Shader,AudioClip}/
- Updated all include paths from relative to <XCEngine/...> format
- Fixed circular dependency in Material.h (removed unnecessary ResourceManager.h include)
- Fixed malformed include syntax in ResourceManager.h and AsyncLoader.h
- Fixed glad.h path issues in CMakeLists.txt

engine/src/Resources/Texture/Texture.cpp

@@ -0,0 +1,40 @@
+#include "Resources/Texture.h"
+#include <cstring>
+
+namespace XCEngine {
+namespace Resources {
+
+Texture::Texture() = default;
+Texture::~Texture() = default;
+
+void Texture::Release() {
+    m_pixelData.Clear();
+    SetInvalid();
+}
+
+bool Texture::Create(Core::uint32 width, Core::uint32 height, Core::uint32 depth,
+                    Core::uint32 mipLevels, TextureType type, TextureFormat format,
+                    const void* data, size_t dataSize) {
+    m_width = width;
+    m_height = height;
+    m_depth = depth;
+    m_mipLevels = mipLevels;
+    m_textureType = type;
+    m_format = format;
+    
+    if (data && dataSize > 0) {
+        m_pixelData.Resize(dataSize);
+        std::memcpy(m_pixelData.Data(), data, dataSize);
+    }
+    
+    m_memorySize = dataSize;
+    
+    return true;
+}
+
+bool Texture::GenerateMipmaps() {
+    return false;
+}
+
+} // namespace Resources
+} // namespace XCEngine