Expand graded algebra and exterior algebra sections

Added detailed definitions and propositions for graded algebras, degree-preserving homomorphisms, and quotient structures. Expanded the construction and functorial properties of tensor and exterior algebras, including explicit functor diagrams and universal properties. Introduced the trace pairing, resultant, and discriminant concepts, with explicit formulas and remarks, and provided a more comprehensive treatment of discriminants for polynomials, bilinear forms, and algebras.

Author: hooyuser