feat: folder system for datasets

[Felipedino]

Summary

• Adds a Folder model (dedicated DB table) with a nullable folder_id FK on Dataset (ondelete="SET NULL" so deleting a folder never deletes its datasets).
• REST endpoints: GET/POST /api/v1/folder, PATCH/DELETE /api/v1/folder/{id}.
• PATCH /api/v1/dataset/{id} extended to accept folder_id (uses model_fields_set to distinguish "not sent" from null).
• Seed datasets are auto-assigned to an "Example datasets" folder on first run.
• New DatasetFolderList component replaces the flat CollapsibleList in both the Datasets/Notebooks and Models sidebars. Features:
  • Collapsible folder sections with dataset count badge.
  • Drag & drop between folders (@dnd-kit/core, 5px activation distance to preserve click/edit).
  • Optimistic UI updates with rollback on failure.
  • Create, rename, delete folders inline (3-dots menu per folder).
  • "No folder" virtual section as drop target for unassigned datasets.
• i18n keys added for all 5 locales (en, es, de, pt, zh).

Migration

Alembic revision f1a2b3c4d5e6 — runs automatically on startup. Uses op.batch_alter_table for SQLite FK compatibility.

Test plan

• alembic upgrade head / alembic downgrade -1 clean round-trip.
• First run: all seed datasets appear under "Example datasets" folder.
• Create a folder, drag a dataset into it — persists on reload.
• Delete a folder — its datasets move to "No folder".
• Click to open dataset and inline rename still work (drag not triggered on click).
• Both sidebars (Datasets/Notebooks and Models) show the folder list.
• pytest tests/back/ and yarn lint pass.

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Additional context or considerations.

[Copilot]

Pull request overview

Introduces a first-class folder system for organizing datasets end-to-end: DB schema + API endpoints + frontend sidebar UI (including drag & drop), with seed-data initialization and i18n updates.

Changes:

• Backend: adds Folder model/table, nullable Dataset.folder_id FK (SET NULL), folder CRUD endpoints, and extends dataset PATCH to accept folder_id.
• Frontend: adds folder API/types/hooks and replaces flat dataset lists in sidebars with a folder-based list supporting DnD and inline folder management.
• Operations/i18n: new Alembic migration, seed datasets assigned to an “Example datasets” folder, and locale strings added across 5 languages.

Reviewed changes

Copilot reviewed 24 out of 25 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
DashAI/front/yarn.lock	Locks new @dnd-kit/* transitive dependencies for drag & drop.
DashAI/front/package.json	Adds @dnd-kit/core dependency for DnD support.
DashAI/front/src/utils/i18n/locales/en/datasets.json	Adds folder-related labels/messages/errors (EN).
DashAI/front/src/utils/i18n/locales/es/datasets.json	Adds folder-related labels/messages/errors (ES).
DashAI/front/src/utils/i18n/locales/de/datasets.json	Adds folder-related labels/messages/errors (DE).
DashAI/front/src/utils/i18n/locales/pt/datasets.json	Adds folder-related labels/messages/errors (PT).
DashAI/front/src/utils/i18n/locales/zh/datasets.json	Adds folder-related labels/messages/errors (ZH).
DashAI/front/src/types/folder.ts	Introduces frontend IFolder type.
DashAI/front/src/types/dataset.ts	Adds folder_id to dataset type.
DashAI/front/src/api/folders.ts	Implements folder REST API client wrapper.
DashAI/front/src/hooks/datasets/useFolders.js	Adds folder state + CRUD hook with snackbar feedback.
DashAI/front/src/hooks/datasets/useDatasets.js	Adds optimistic dataset move-to-folder action.
DashAI/front/src/components/threeSectionLayout/DatasetFolderList.jsx	New folder-aware sidebar list with DnD + inline folder CRUD UI.
DashAI/front/src/components/notebooks/DatasetNotebookLeftBar.jsx	Swaps dataset list to DatasetFolderList and wires folder actions.
DashAI/front/src/components/models/ModelsLeftBar.jsx	Swaps dataset list to DatasetFolderList and wires folder actions.
DashAI/front/src/components/models/ModelsContext.jsx	Exposes folder state/actions in models context and triggers initial fetch.
DashAI/front/src/components/custom/contexts/DatasetsAndNotebooksContext.jsx	Exposes folder state/actions in datasets/notebooks context.
DashAI/back/dependencies/database/models.py	Adds Folder ORM model and Dataset.folder_id relationship/FK.
DashAI/back/api/api_v1/schemas/folders_params.py	Adds Pydantic schemas for folder create/update/response.
DashAI/back/api/api_v1/schemas/datasets_params.py	Extends dataset schemas to include folder_id.
DashAI/back/api/api_v1/endpoints/folders.py	Adds folder CRUD endpoints under /api/v1/folder.
DashAI/back/api/api_v1/endpoints/datasets.py	Extends dataset PATCH endpoint to handle folder_id.
DashAI/back/api/api_v1/api.py	Registers the new folders router.
DashAI/back/seeds/init.py	Creates “Example datasets” folder and assigns seeded datasets to it.
DashAI/alembic/versions/f1a2b3c4d5e6_add_folder_system.py	Migration creating folder table and adding dataset.folder_id FK.

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[Copilot]

Pull request overview

Copilot reviewed 24 out of 25 changed files in this pull request and generated 4 comments.