Cosmic Topology: Geometric Unification of Spatial Overlap, Material Structure, and Gravity (Version 3.0 — Final)

This paper establishes Cosmic Topology (Spatial Geometry of Cosmic Unification, SGCU) with full mathematical rigor. The central postulate is: three-dimensional space may undergo multi-layer overlap within the same region, and this overlap itself constitutes the common geometric origin of mass, energy, and interactions. We provide a strict axiomatic definition of spatial overlap, construct a 3+1-dimensional field-theoretic model, prove the existence of soliton solutions, and derive the discrete mass spectrum. Within a unified framework, we derive the cosmic composition structure and present a geometric interpretation of the four fundamental interactions. The single core prediction of the theory is that the photon possesses a non-zero rest mass, the value of which is rigorously derived from the theory, accompanied by a clear experimental falsification condition.