PS25: Customer Segmentation K-Means

Dataset source expected: Mall_Customers.csv. Add the actual dataset CSV to dataset/; if it is absent, a labelled generated practice dataset is used. Covers missing values, scaling, elbow curve, K-Means, cluster counts, visualization and cluster profiles.
REFERENCE PDF UPDATE
This solution.py has been revised to follow the approach/code structure in the uploaded 68-page reference PDF where a matching assignment exists. See the comments at the top of solution.py.
