Feat/export dataset metrics

[Creylay]

Summary

Add per-card multi-format export capabilities to dataset analysis cards. Each card now has a download menu
offering image (full card or chart-only), CSV, and JSON export options via a reusable ExportableCard component.

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Type of Change

Check all that apply like this [x]:

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

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Changes (by file)

• src/components/notebooks/dataset/ExportableCard.jsx: New reusable component wrapping MUI Card with a
  download icon that opens a menu with 4 export options — card as image, chart as image, CSV, and JSON. Uses
  html2canvas for image capture and auto-detects recharts/plotly containers for chart-only exports.
• src/components/notebooks/dataset/tabs/NumericTab.jsx: Replaced Card with ExportableCard, passing column
  stats as exportData.
• src/components/notebooks/dataset/tabs/TextTab.jsx: Replaced Card with ExportableCard, passing column
  stats as exportData.
• src/components/notebooks/dataset/tabs/CategoricalTab.jsx: Replaced Card with ExportableCard, passing
  column stats as exportData.
• src/components/notebooks/dataset/tabs/CorrelationsTab.jsx: Replaced Card with ExportableCard, passing
  correlation data as exportData.
• src/components/notebooks/dataset/tabs/QualityTab.jsx: Replaced both Card elements with ExportableCard,
  passing quality info and missing data ratios as exportData.
• src/components/notebooks/dataset/tabs/OverviewTab.jsx: Replaced only the Missing Values Overview card with
  ExportableCard; Dataset Preview and Column Types Distribution remain as plain Card.
• src/utils/i18n/locales/en/datasets.json: Added translation keys for exportCardImage, exportChartImage,
  exportCSV, exportImage, exportJSON.
• src/utils/i18n/locales/es/datasets.json: Added corresponding Spanish translations.

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Testing (optional)

• Verify the download icon appears on all analysis cards (Numeric, Text, Categorical, Correlations, Quality,
  Missing Values Overview).
• Verify it does not appear on Dataset Preview or Column Types Distribution cards.
• Test each menu option: card as image, chart as image, CSV download, and JSON download.
• Confirm CSV and JSON options only appear on cards where exportData is provided.

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Notes (optional)

• The ExportableCard component detects charts at runtime by querying for .recharts-wrapper or
  .js-plotly-plot DOM elements within the card.
• Cards without charts will still show the "Chart as image" option but it will be a no-op if no chart element is
  found.