fix: migrate the unique_id of the service entities (#1778)

The description of the service was appended to the unique_id of the service
entities without a migration step, so the entities registered before that
change were replaced by new ones. The entity_id of the new entity is
different, which silently breaks every automation, script and dashboard
referring to the old one.

Look up the entities that are still registered under the old unique_id when
the entry is set up, and rewrite it in place. The entity_id is left
untouched, so nothing referring to it has to be updated.

The lookup is keyed on the unique_id only and scoped to the config entry, and
nothing is written when the current unique_id is already registered, so it is
idempotent and cannot replace an entity that is in use. An entity that cannot
be migrated is reported and skipped, the others are still migrated.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

custom_components/xiaomi_home/miot/miot_device.py

@@ -380,6 +380,18 @@ class MIoTDevice:
             f'{ha_domain}.{self._model_strs[0][:9]}_{self.did_tag}_'
             f'{self._model_strs[-1][:20]}_s_{siid}_{description}')
 
+    def gen_service_entity_id_legacy(
+        self, ha_domain: str, siid: int
+    ) -> list[str]:
+        """Return the service entity ids generated by previous versions.
+
+        The description of the service was appended to the id, an entity
+        registered before that change is still stored under the id without it.
+        """
+        return [
+            f'{ha_domain}.{self._model_strs[0][:9]}_{self.did_tag}_'
+            f'{self._model_strs[-1][:20]}_s_{siid}']
+
     def gen_prop_entity_id(
         self, ha_domain: str, spec_name: str, siid: int, piid: int
     ) -> str: