fix: add default values to optional switch/select templates in HA component

Same fix as bridge — fields like bzr, acec, acpm, acng, acdc, cnv are
not present in all device status payloads (model-dependent), causing
HA template warnings on every status update.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Amit Seth

custom_components/kpr_miraie_mqtt/coordinator.py

@@ -305,7 +305,7 @@ def _build_discovery(self, device_id: str, dev: dict) -> list[tuple]:
                 "object_id": f"{slug}_{key}",
                 "device": device_block,
                 "state_topic": status_topic,
-                "value_template": f"{{{{ value_json.{key} }}}}",
+                "value_template": f"{{{{ value_json.{key} | default('off') }}}}",
                 "state_on": "on",
                 "state_off": "off",
                 "command_topic": control_topic,
@@ -361,7 +361,7 @@ def _build_discovery(self, device_id: str, dev: dict) -> list[tuple]:
             "object_id": f"{slug}_converti",
             "device": device_block,
             "state_topic": status_topic,
-            "value_template": "{{ value_json.cnv }}",
+            "value_template": "{{ value_json.cnv | default('0') }}",
             "command_topic": control_topic,
             "command_template": '{"cnv":{{ value }},"ki":0,"cnt":"an","sid":"0"}',
             "options": ["0", "40", "50", "60", "70", "80", "90", "100", "110"],