[Domain] flag walls and obstacles blocking connection passages

[SilverSupplier]

Summary

• Add layout import validation that flags a movement-blocking wall or obstacle whose geometry crosses the interior of a connection passage (new ImportIssueCode::ObstructedConnection, reported as a non-blocking warning). This closes the previously missing "walls/obstacles must not conflict with the space structure" validation item.
• Crossings at span endpoints (doorways meeting flanking walls) and boundary-parallel walls are excluded so valid layouts are not falsely flagged.
• Wire the new code into application-side live re-validation so it refreshes while the layout is edited.
• Add tests/ImportValidationServiceTests.cpp: clean-layout baseline, a wall crossing a passage, a non-blocking barrier (ignored), and an endpoint-contact wall (ignored).

Area

• Domain
• Application

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)

Ran the release / no-app equivalents: cmake --preset windows-release-no-app, cmake --build --preset build-no-app-release, ctest --preset test-no-app-release -> 100% pass (includes the new ImportValidationServiceTests). The full Qt app build (cmake --build --preset build-release --target safecrowd_app) also succeeds.

Risks / Follow-up

• The new issue is a non-blocking warning, so it surfaces for review without rejecting layouts. Tolerances exclude endpoint contact and boundary-parallel walls to avoid false positives on existing demo/test fixtures.