Add 6 features: mode-click->UMAP, food-group filter, why-explainers, recipe builder, public API, saved queries (BrowserState)

Add matplotlib to requirements (was missing for the new heatmap)

Add UMAP visualisation, fridge parser, basket cosine heatmap (8 tabs total)

Bump Gradio to 5.x and add audioop-lts shim for Python 3.13 compatibility

Initial release: Epicure Explorer Gradio demo. Paper arxiv 2605.22391.