Add publication-ready documentation and reproducible experiment package.

Rewrite the README with secure setup instructions, add dedicated setup/security docs, and include the standalone local-volatility instability experiment materials for reproducible analysis.

Made-with: Cursor

.gitignore

@@ -0,0 +1,24 @@
+# Built Python extension dropped next to qengine/__init__.py for local dev
+/qengine/*.so
+/qengine/*.dylib
+/qengine/__pycache__/
+
+/skbuild-build/
+
+/build/
+/.idea/
+**/__pycache__/
+/docs/html/
+/docs/latex/
+
+# Local reference tree (optional clone)
+/CPP-design-pattern-derivatives-pricing/
+
+# Local environment and secrets
+.env
+.env.*
+!.env.example
+
+# Local tooling caches
+/.pycache/
+/.mplconfig/