[awais-ur-rehman]

Summary

Add a runnable case study that passes a compiled SymEngine expression to SciPy's nquad, compares it with a Python callback, and checks both results against the exact integral. Connect the case study to the tutorial navigation and add SciPy to both tutorial environments.

Fixes #13.

Breaking changes

None.

Testing

• Executed all three code cells with SymEngine 0.14.1 and SciPy 1.17.1. Both callbacks returned 0.2000000000189363, and the exact-value and agreement assertions passed.
• Confirmed the same Lambdify(..., as_scipy=True) integration API is covered by test_scipy in the pinned SymEngine 0.6.1 source; did not run that older environment locally.
• Built the full site with Sphinx 9.0.4 and MyST-NB 1.4.0, including execution of the Python notebooks. A temporary config skipped C++ notebook execution because the local environment has no xcpp11 kernel; the build and baseline each reported 18 warnings from existing documentation/configuration.
• Checked the rendered tutorial in a browser, including its numerical outputs and navigation, and verified the generated local link targets on all three affected pages.
• To verify manually, open Tutorials → Case Studies → Numerical integration with SciPy, then run the notebook cells in order.