feat v1.12.0: Quality Scale conformance (phases 7-8)

- entry.runtime_data (HouseplanData in store.py) instead of hass.data; WS answers
  not_ready without a loaded entry
- test-before-setup (ConfigEntryNotReady), async_unload_entry, async_remove_entry
  (Lovelace resource cleanup), single_config_entry in manifest
- Store minor_version + migration hook; diagnostics.py (redacted); repairs
  (broken_plan issues, en/ru); system_health.py; strings.json
- quality_scale.yaml self-assessment; HA-harness tests (config flow, WS, upload)
  in CI on py3.13; CI backend job updated

tests_backend/conftest.py

@@ -0,0 +1,19 @@
+"""Shared fixtures. HA-harness tests are skipped when homeassistant is not installed
+(the local sandbox has Python 3.10; CI runs them on 3.13 with
+pytest-homeassistant-custom-component)."""
+import pytest
+
+try:
+    import homeassistant  # noqa: F401
+    HAS_HA = True
+except ImportError:
+    HAS_HA = False
+
+collect_ignore_glob = [] if HAS_HA else ["test_ha_*.py"]
+
+
+if HAS_HA:
+    @pytest.fixture(autouse=True)
+    def auto_enable_custom_integrations(enable_custom_integrations):
+        """Allow loading custom_components in the test hass."""
+        yield