replace curve in ecpoint with a reference

[steven-varga]

Replace curve::C in ECPoint{T,C} with reference to reduce memory usage

Description:

Currently, the ECPoint struct stores a full copy of the curve object:

struct ECPoint{T, C<:Curve}
    point::Point{T}
    curve::C
end

In many cases, especially for static or singleton curves (e.g. base points on a known curve), this results in unnecessary duplication and increased memory pressure. Holding a reference to the curve (or even using a shared singleton via const or Ref) could significantly reduce the memory footprint without impacting correctness.

Proposal:

Refactor ECPoint to hold a reference or shared handle to the curve object. Some ideas:

• Use const GLOBAL_CURVE = ... and pass reference to that
• Change curve::C → curve::Ref{C} or curve::Base.RefValue{C}
• Use a parametric singleton pattern if curve data is constant

New structure could look like:

struct ECPoint{T, C<:Curve}
    point::Point{T}
    curve::Ref{C}  # or Base.RefValue{C}
end

Tasks:

• Benchmark construction and point arithmetic with current curve::C
• Measure memory overhead for large sets of ECPoints
• Evaluate design options (immutable singleton vs reference container)
• Implement the chosen strategy
• Test impact on performance and garbage collection

Motivation:

• Reduce per-point memory footprint
• Enable more efficient curve-based cryptographic structures
• Lay the groundwork for supporting large batches of points over the same curve