feat: entity actions menus — notebooks, share icons, report issue, bookmark

[HelderMendes]

Introduces a standardized actions menu and report issue dialog for entity pages (Datasets, Collections).

New components

• EntityActionsMenu — reusable dropdown for entity actions (Share, Open in Notebook, Report Issue) for Tasks, Flows, Runs, Collections, Benchmarks and Measures
• DatasetActionsMenu — dataset-specific actions extending the shared menu, adds Bookmark and Add to Collection (requires auth session)
• ReportIssueDialog — dialog for reporting issues directly from an entity page

Page updates

• collections/[id]/page.tsx — integrated the new actions menu

Dependencies

• package.json - new components