Add C code generation for implicit parametric DAQP solver

[Copilot]

Implements the missing C code generation needed to deploy a compiled parametric QP solver using DAQP, given an mpQP defined via a JuMP/MOI model.

Changes

Merged double-sided branch foundation

• preprocess.jl: equality elimination and double-sided → single-sided conversion
• MathOptInterfaceExt.jl: moi2mpqp extracts a double-sided mpQP from a MOI model; get_mpp exposes this to users
• JuMPExt.jl: forwards get_mpp and updated mpsolve to JuMP models

Implemented C code generation in render_pdaqp_workspace

Three C functions are now emitted by codegen_implicit:

pdaqp_update_qp — updates DAQP's LDP bounds for a given parameter vector:

dupper[i] = du[i] + Dth[i*N_PARAMETERS + j]*th[j];
dlower[i] = dl[i] + Dth[i*N_PARAMETERS + j]*th[j];

pdaqp_get_solution — affine back-transform from the DAQP QP solution to the nominal variable:

solution[i] = xstar[i] + Z_offset[i + j*N_DECISION]*th[j] + z_offset[i];

pdaqp_compute_solution — top-level entry point: updates bounds, resets workspace (skipped if warm_start=true), calls daqp_ldp + ldp2qp_solution, then applies the back-transform.

Header generation fixes

• Added PDAQP_N_CONSTRAINTS and PDAQP_N_DECISION #defines
• Added function declarations for all three new functions
• Corrected output-variable count to use size(mpldp.HinvF, 2) (respects out_vars selection)
• Added #include "daqp.h" in the generated source for DAQP workspace access

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