Complete memory leak fix: add dealloc(m_imp) to lar_solver destructor

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

Author: Copilot

src/math/lp/lar_solver.cpp

@@ -232,6 +232,7 @@ namespace lp {
         for (auto t : m_imp->m_terms)
             delete t;
         m_imp->m_var_register.clear();
+        dealloc(m_imp);
     }
 
     void lar_solver::clear_columns_with_changed_bounds() { m_imp->m_columns_with_changed_bounds.reset(); }