feat: integrate Google Earth 3D Tiles and optimize engine hooks

Introduce structure registry and fix content loader

Fix stall physics, tracer visibility, net packet size, and type modularization

Fix invisible bullets and particles by enabling vertexColors on instanced materials and pre-allocating instanceColor attributes

Optimize particle draw calls via InstancedMesh and remove FPV transition shader recompilation lag

Refactor codebase to under 150 lines per file; reduce FPV turbulence and adjust cockpit scaling