[Application] Left navigation tree context menu actions

[95x8x9]

Summary

• Adds right-click context menus to left navigation trees (Layout/Crowd/Events) to allow Delete, plus Settings where applicable.
• Fixes a crash caused by parenting a stack-allocated QMenu to the tree while the navigation panel is being replaced.

Related Issue

• None (application-only PR)

Area

• Engine
• Domain
• Application
• Docs
• Build
• Analysis
• Chore

Architecture Check

• I kept the dependency direction application -> domain -> engine.
• I did not add Qt UI code to src/domain.
• I did not add domain or application dependencies to src/engine.
• I used src/ as the include root.

Verification

• cmake --preset windows-debug
• cmake --build --preset build-debug
• ctest --preset test-debug
• Not run (reason below)

Risks / Follow-up

• Operational event Settings currently edits the name/trigger/target summaries via a simple dialog; future work may replace this with a richer inspector UI.