Use BLE device name, add hard poll timeout, tighten request timing

- Device name: coordinator now takes name=entry.title so the HA device card
  shows the actual BLE advertised name instead of "Xiaoxiang Smart BMS"
- Hard poll timeout: each poll is capped at (poll_interval - 3)s via
  asyncio.wait_for so a stalled poll can't bleed into the next cycle
- Request timeout: 5s → 3s (BMS should reply in <1s under normal conditions)
- Retry delay: 0.5s → 0.3s between retries

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

custom_components/xiaoxiang_bms/__init__.py

@@ -15,7 +15,7 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
     address = entry.data[CONF_ADDRESS]
     poll_interval = entry.options.get(CONF_POLL_INTERVAL, DEFAULT_POLL_INTERVAL)
 
-    coordinator = BmsCoordinator(hass, address, poll_interval)
+    coordinator = BmsCoordinator(hass, address, poll_interval, name=entry.title)
     await coordinator.async_setup()
     await coordinator.async_config_entry_first_refresh()