feat: replace MQTT bridge with localthings HA custom component

Convert from MQTT bridge architecture to a proper Home Assistant
integration (custom_components/localthings/):

- Config flow: IP-only entry, probes ports [49154,49155], cert/key
  reused from first device on subsequent adds
- Coordinator: DataUpdateCoordinator wrapping blocking DTLS session
  via async_add_executor_job; discovery on first poll; dynamic 5s/30s
  interval based on active_when
- Entity platforms: sensor, binary_sensor, switch, number, select
- Library cleanup: delete bridge.py, main.py, config.py, logger.py,
  keepalive.py, poll_scheduler.py, sensors.py, state_cache.py
- adapter.py stripped to flatten(), is_active(), _key()
- _parse_device0_batch moved to samsung_appliance/batch.py

tests/conftest.py

@@ -7,8 +7,8 @@ FIXTURES = Path(__file__).resolve().parent / 'fixtures'
 
 
 def _resources_from_dump(dump: dict) -> dict[str, dict]:
-    from samsung_appliance.bridge import _parse_device0_batch
-    return _parse_device0_batch(dump['device0'])
+    from samsung_appliance.batch import parse_device0_batch
+    return parse_device0_batch(dump['device0'])
 
 
 def _load_device(name: str) -> dict[str, dict]: