feat: depth buffer + 3D model matrix — rotating cube now looks correct

- Depth image (D32_SFLOAT) + image view created in VulkanSwapchain
- VkPipelineDepthStencilStateCreateInfo: depth test + write enabled, CompareOp=Less
- Push constant changed from float angle (4B) to mat4 model (64B)
- 3D rotation: RotateY * RotateX in renderer, applied via push constant
- Vertex shader: gl_Position = vp * model * vec4(pos, 1.0)
- Depth attachment in VkRenderingInfo + depth clear (1.0)
- Depth image layout transition (Undefined → DepthStencilAttachmentOptimal)
- New Vulkan functions: vkCreateImage, vkDestroyImage, vkGetImageMemoryRequirements, vkBindImageMemory
- New structs: VkPipelineDepthStencilStateCreateInfo, VkStencilOpState, VkImageCreateInfo
- New enums: VkCompareOp, VkImageType, VkImageTiling
- 0 validation errors

src/Engine.Graphics.Vulkan/VulkanRenderContext.cs

@@ -23,7 +23,7 @@ internal sealed class VulkanRenderContext : IRenderContext
         };
 
         _swapchain = new VulkanSwapchain(_ctx.Device, _ctx.PhysicalDevice, _ctx.Surface,
-            surfaceFormat, window.Width, window.Height);
+            surfaceFormat, window.Width, window.Height, _ctx);
     }
 
     public IRenderer CreateRenderer()