Show authorized related items and backlinks in the interface #90

Work

Display compact Related/Referenced by sections in memory/task details, with type, public number and authorized title. Support creating/removing explicit relations with clear semantics. Keep original context/history navigation and paginate large lists.

Acceptance

• User can follow task -> implementing decision -> tasks referencing it.
• Titles/counts do not reveal inaccessible sources or targets.
• Missing/archived items have clear permitted behavior.
• Keyboard, narrow screens and long titles work without oversized headers or pills.

Dependencies

Persisted relations under #75; use existing palette and compact typography.