feat(): add Associated Datasets UI prototype Qwen3.7 Plus

[sven1103]

Add a pure UI prototype for the 'Connect datasets with research projects' feature (Stories 01-08), demonstrating search, connect, view, sync, and remove interactions for open and restricted datasets on InvenioRDM instances (Zenodo, FDAT).

Files added:

• datamanager-app/.../demo/AssociatedDatasetsDemo.java: Development-profile-only Vaadin view at /test-view/associated-datasets with a Public/Restricted tab layout, mock data, and inline actions.
• docs/feature-vision-associated-datasets.md: Reformatted feature vision document with background, scope, and user stories.
• ui-screenshot(-restricted).png: Visual reference of the prototype for PR review.

The demo uses existing project UI patterns (Section, ActionBar, InfoBox, Tag, TabSheet) and requires no real backend integration.

Description

Issue and Traceability

Linked Task Issue

• Closes: #

Requirement IDs Addressed

• Requirement IDs:

Requirement Update Status

• Requirements Updated: The corresponding functional/non-functional requirements in docs/requirements.md have been updated to reflect this implementation.
• Justification Provided: This PR does not change externally observable behavior, so no requirement update is needed. (Provide brief justification below)

Justification (if applicable)

Changes Summary

Modified Areas

• Domain layer (domain/model/, domain events, aggregates)
• Application layer (application/ services, use cases)
• Infrastructure layer (JPA repositories, external integrations, config)
• UI / Views (views/ components, Vaadin routes)
• Database schema (sql/, DDL changes)
• Tests (unit, integration, or Spock specs)
• Documentation, CI/CD, or build configuration
• Other (describe):

Behavioral Changes

• No behavioral changes (internal refactoring, optimization, test addition, etc.)
• Yes, behavior changes:

Sensitive Changes Requiring Review

• Database schema changes (sql/complete-schema.sql, table/column DDL)
• Spring Security configuration (security/, ACL setup, authentication/authorization)
• FAIR / RO-Crate export format (docs/fair/, RO-Crate builder logic)
• Artemis messaging topics (JMS topic names, consumer configuration)
• Requirement file edits (docs/requirements.md)
• None of the above

Pre-Submission Checklist

• Issue Linked: PR references a Task issue (see "Linked Task Issue" section above)
• Requirements Listed: All functional (R) and non-functional (NFR) requirement IDs are listed above
• No Constraint IDs: No C (constraint) IDs are listed in the Requirement IDs section
• Behavior vs. Requirements: Requirement update confirmed OR explicit justification provided
• Code Style: Code follows Google Java Style Guide (run formatter before commit)
• Tests: New tests added or existing tests updated to cover changes
• No Secrets: No hardcoded credentials, API keys, passwords, or secrets committed
• Documentation: Updated relevant docs if the change affects user-facing behavior or public APIs

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Notes for Reviewers