Replace sidebar action buttons with hub buttons across modules

[Creylay]

Summary

Replaced the "New Dataset/Notebook", "New Session", and "Create a session" buttons in the Datasets, Models, and Generative sidebars with hub-style buttons ("Dataset Hub", "Models Hub", "Generative Hub"). The buttons now use the ViewModule icon to signal navigation to a central resource hub. Also improved NewItemButton to support custom icons and prevent text overflow with ellipsis truncation.

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Type of Change

• Backend change
• Frontend change
• CI / Workflow change
• Build / Packaging change
• Bug fix
• Documentation

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Changes (by file)

• components/threeSectionLayout/NewItemButton.jsx: added EndIcon prop for custom icons (defaults to AddIcon); added ellipsis truncation for long labels button with "Dataset Hub" using ViewModuleIcon
• components/models/ModelsLeftBar.jsx: replaced "New Session" button with "Models Hub" using ViewModuleIcon
• components/generative/SessionBar.jsx: replaced "Create a session" button with "Generative Hub" using ViewModuleIcon
• locales/{en,es,pt,de}/datasets.json: added datasetHub translation key
• locales/{en,es,pt,de}/models.json: added modelsHub translation key
• locales/{en,es,pt,de}/generative.json: added generativeHub translation key