refactor: centralize dataset polling and remove redundant fetchDatase…

[Creylay]

Summary

Refactored dataset status updates to use a single centralized polling flow instead of component-level polling triggers. This removes duplicated polling behavior when datasets are processing and keeps both the left dataset list and DatasetVisualization in sync from shared state.

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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)

• DashAI/front/src/hooks/datasets/useDatasets.js:
  • Centralized dataset refresh behavior using job updates (subscribeJobs)
  • Made fetchDatasets stable and based on a ref-backed latest dataset snapshot
  • Removed extra fetchDatasets() call from startDatasetPolling success callback (now selection/snackbar only)
• DashAI/front/src/components/DatasetVisualization.jsx:
  • Removed local polling trigger (setTimeout(fetchDatasets, 1000))
  • Simplified effect to react to dataset changes and fetch dataset info only
  • Removed unused fetchDatasets prop
• DashAI/front/src/components/notebooks/dataset/DatasetsCenterContent.jsx:
  • Removed passing fetchDatasets prop into DatasetVisualization

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Testing (optional)

1. Start uploading/processing a dataset and open the dataset module.
2. Verify dataset status updates in the left list while processing.
3. Verify DatasetVisualization updates correctly when processing finishes.
4. Confirm no duplicated polling behavior (fewer duplicate refreshes/requests).