implement schoof–elkies–atkin algorithm

[steven-varga]

Summary:
Implement the SEA algorithm to efficiently count the number of points on elliptic curves over large prime fields, enabling secure curve generation at 128-bit and higher security levels.

Details:
Input: Elliptic curve over 𝔽ₚ, where p is a large prime (e.g. 256-bit).
Output: Trace t of Frobenius, so that the number of points #E(𝔽ₚ) = p + 1 - t.

Tasks:
Implement modular polynomial generation for Elkies primes.
Compute kernel polynomials and eigenvalues of Frobenius.
Combine using CRT to recover the trace modulo lcm(ℓ_i).

References:
Schoof–Elkies–Atkin algorithm