Add volume management system for spatial acceleration of scene traversal and culling

[Copilot]

Introduces octree-backed spatial volume management to replace linear primitive iteration during frustum culling and spatial queries.

Core geometry additions

• Sphere intersections (Shapes.h/.cpp): Sphere-Plane, Sphere-AABB, Sphere-Frustum
• AABB helpers (AABB.h): GetCenter(), GetExtent(), IsValid(), Contains()
• BoundingVolume (BoundingVolume.h): Type-erased wrapper over AABB/Sphere with frustum/AABB intersection dispatch

OctTree extension

• Added ForeachWithNodeTest — generic traversal with a caller-supplied node-level predicate, enabling early subtree rejection (e.g. frustum vs node AABB)

VolumeManager (VolumeManager.h)

• unordered_map<VolumeID, VolumeEntry> for O(1) lookup with pointer stability
• Octree<VolumeEntry*> for spatial partitioning — pointers into the map, so octree IndexChanged callbacks update the canonical entry directly
• FrustumCull: octree-accelerated traversal that skips entire subtrees outside the frustum, then refines per-element
• QueryByAABB: delegates to existing octree bound test
• AddVolume / RemoveVolume / UpdateVolume (remove + re-insert)

Render pipeline integration

• RenderScene owns a VolumeManager; AddPrimitive/RemovePrimitive auto-register volumes
• RenderPrimitive carries a volumeId for tracking
• MeshRenderer::UpdateTransform syncs world bounds into the volume manager

// Frustum culling now uses octree acceleration
volumeManager.FrustumCull(frustum, [](const VolumeEntry &entry) {
    auto *prim = static_cast<RenderPrimitive*>(entry.userData);
    // primitive is visible
});

// Spatial queries (e.g. overlap tests, proximity)
volumeManager.QueryByAABB(queryBox, [](const VolumeEntry &entry) {
    // entry intersects queryBox
});

Tests

test/core/VolumeTest.cpp covers AABB helpers, all new intersection functions, BoundingVolume dispatch, and VolumeManager operations (add/remove/update/frustum cull/AABB query/user data).

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