Restructure C++ core into cpp module and package bindings.

Move the pricing engine sources out of src/ into cpp/, add the closed-form engine and pybind wiring, and align tests/build targets with the new project layout.

Made-with: Cursor

cpp/BSWrapper.hpp

@@ -0,0 +1,24 @@
+/**
+ * @file BSWrapper.hpp
+ * @brief Black–Scholes vanilla price (closed form; used from Python / implied vol).
+ */
+
+#ifndef QUANTENGINE_BSWRAPPER_HPP
+#define QUANTENGINE_BSWRAPPER_HPP
+#include <vector>
+
+/**
+ * @brief Static helpers wrapping scalar and batch pricing.
+ */
+class BSWrapper {
+public:
+    BSWrapper() = delete;
+    static double bs_price_wrapper(double S, double K, double T, double r, double sigma, bool is_call);
+    static std::vector<double> batch_bs_price_wrapper(const std::vector<double>& S, const std::vector<double>& K,
+        const std::vector<double>& T, const std::vector<double>& r, const std::vector<double>& sigma,
+        const std::vector<bool>& is_call);
+
+};
+
+
+#endif //QUANTENGINE_BSWRAPPER_HPP