Add pip/uv install instructions to README

Update README with all new features and add example images

Rewrite getting_started notebook as a full library walkthrough

Add plot_neuron_indices visualization

Add mexican hat neighborhood function

Add per-neuron quality map visualization (plot_quality_map)

Add label map visualization (plot_label_map)

Add online/sequential training via fit_online

Add model save/load via pickle

Optimize topographic error and add training progress plot to notebook

Add collect_history param for per-epoch training progress tracking

Add mapsize_scale param to SOM and estimate_mapsize

Revamp fit_auto with optimized defaults from autoresearch

Add subsample_ratio param to fit/train_som

Add learning_rate param to fit/train_som