feat(mesh): Mesh Loading System — OBJ parser, 3D components (RF5.2)

[LyeZinho]

Summary

• Implements RF5.2: Mesh Loading System with OBJ parser and 3D spatial components
• Adds Components3D.hpp (Position3D, Rotation3D, Scale3D)
• Adds MeshTypes.hpp (Vertex3D, Mesh3D, Material3D, MeshRenderer)
• Adds MeshLoader.hpp with OBJ parser and MeshSystem
• 24 tests in test_mesh.cpp covering all components and OBJ parsing

Files

File	Change
src/ecs/Components3D.hpp	New — Position3D, Rotation3D, Scale3D components
src/assets/MeshTypes.hpp	New — Vertex3D, Mesh3D, Material3D, MeshRenderer, Color, Rect3D
src/assets/MeshLoader.hpp	New — MeshLoader (OBJ parser), MeshSystem : ECS::ISystem
tests/test_mesh.cpp	New — 24 tests, always compiled (no SDL3 dep)
src/Caffeine.hpp	Mesh includes added
tests/CMakeLists.txt	test_mesh.cpp added to base sources
docs/fase5/mesh-loading.md	Status → ✅, API rewritten to match implementation

Design Notes

• MeshLoader::parseOBJ() supports all OBJ face formats: v/vt/vn, v//vn, v/vt, v
• Negative indices in OBJ files supported (relative indexing)
• Face triangulation via fan algorithm (for N-gons)
• MeshLoader::fromMemory() creates mesh from raw vertex/index arrays
• computeBounds() calculates AABB for frustum culling
• GPU upload code guarded with #ifdef CF_HAS_SDL3
• Rotation3D quaternion defaults to identity (0,0,0,1)
• Scale3D defaults to uniform scale (1,1,1)
• Material3D roughness defaults to 0.5f (PBR middle ground)
• All structs default-constructible and safe for CPU-only builds