feat: reimplement Scene domain with create, apply, and delete support

[Faerkeren]

Summary

• Add delete() method to Scene for removing dynamically-created scenes via scene.delete service
• Add create_scene() to HAClient for creating dynamic scenes via scene.create service, returning a Scene instance
• Add apply_scene() to HAClient for applying entity states without persisting via scene.apply service
• Add sync wrappers (create_scene, apply_scene) to SyncHAClient
• Add Scene domain to mkdocs documentation

Changes

File	Change
src/haclient/domains/scene.py	Added delete() method
src/haclient/client.py	Added create_scene() and apply_scene()
src/haclient/sync.py	Added sync wrappers for new client methods
tests/test_client.py	4 new tests for create/apply scene
tests/test_domains.py	1 new test for scene delete
tests/test_sync.py	2 new tests for sync wrappers
docs/reference/domains/scene.md	New mkdocstrings page
mkdocs.yml	Added Scene to nav

All checks pass: lint, mypy, 188 tests, 95.34% coverage.