feat(dashboard): add bulk study actions with progress and reliable sync

[mohiuddinshahrukh]

Summary

Adds bulk study actions to the dashboard and makes their execution more reliable and transparent.

What changed

• Added row selection to the studies table, including select/deselect and select all.
• Added bulk actions for selected studies:
  • export
  • duplicate
  • delete
• Moved bulk actions into a single Bulk actions dropdown.
• Added loading and progress feedback during bulk operations.
• Disabled interaction while a bulk action is running.
• Improved bulk export feedback:
  • export only runs when triggered by the user
  • studies that cannot be exported are skipped
  • the UI reports which studies were skipped and why
• Improved bulk delete reliability:
  • wait for persisted backend completion
  • refresh study data after delete/duplicate
  • only report deletion as successful when backend state confirms it
• Improved delete failure messaging for backend conflicts, including user-friendly handling for studies that still have invite codes linked to them.

Technical changes

• Updated dashboard selection and bulk-action state handling.
• Added progress counters for long-running bulk operations.
• Updated repository delete/duplicate paths to support non-optimistic persisted operations for bulk flows.
• Preserved backend error details from API delete calls so the UI can show more meaningful failure reasons.

Files touched

• designer_v2/lib/features/dashboard/dashboard_controller.dart
• designer_v2/lib/features/dashboard/dashboard_page.dart
• designer_v2/lib/features/dashboard/dashboard_state.dart
• designer_v2/lib/features/dashboard/studies_table.dart
• designer_v2/lib/features/dashboard/studies_table_column_header.dart
• designer_v2/lib/features/dashboard/studies_table_item.dart
• designer_v2/lib/features/analyze/study_export_zip.dart
• designer_v2/lib/repositories/api_client.dart
• designer_v2/lib/repositories/model_repository.dart
• designer_v2/lib/repositories/study_repository.dart

Validation

• Bulk action controls appear only when studies are selected.
• Bulk actions run with a visible in-progress state and progress count.
• Export reports skipped studies with reasons instead of silently failing.
• Delete no longer claims success based only on local UI state.
• Dashboard data is refreshed after delete and duplicate operations.

[johannesvedder]

Thanks! I already gave feedback on this, why it is not a good idea to include bulk actions.

[mohiuddinshahrukh]

Thanks for the feedback!