[Domain] define import contracts from raw import to FacilityLayout2D

[learncold]

Summary

• add Sprint 1 import domain contracts for raw import, canonical geometry, facility layout, issues, and import orchestration
• preserve raw-source structure and layout provenance so follow-up DXF import and validation work can map source entities to domain results
• gate simulation readiness on explicit import review approval and cover the new contract surface with smoke tests

Related Issue

• Closes Task-define import domain contracts from raw import to FacilityLayout2D #53

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

• #54 still needs the DXF happy-path adapter implementation against these contracts.
• #55 still needs layout inference and validation logic on top of the new DTO surface.