Fix cardinality notebook execution

[mirkovicdev]

Summary

• Fix notebook clustering to return asset-index clusters used by downstream CCMV routines
• Correct cardinality allocation arguments and rounding so allocations sum to Delta
• Replace unavailable CVXPY/MIQP dependency with a SciPy subset-enumeration optimizer for small examples
• Add requirements.txt and update README dependency instructions

Testing

• Installed dependencies with python3 -m pip install -r requirements.txt
• Ran deterministic smoke test that executes notebook code cells and verifies delta_ccmv returns feasible weights summing to 1, respecting bar_w, and using at most Delta assets