Add Vulkan backend scaffolding and default to Vulkan

[ErfanMo77]

Summary

• add a Vulkan renderer backend with dynamic rendering, synchronization2 submission, and swapchain management, making Vulkan the default API
• implement Vulkan-aware resource scaffolding (buffers, vertex arrays, shaders, textures, framebuffers, uniform buffers) and wire RenderCommand/creation helpers to use them
• update window/context creation, guard OpenGL-only render paths, and link against the Vulkan SDK in the build configuration

Testing

• Not run (not requested)

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Codex Task