Initial commit: Xiaoxiang Smart BMS Home Assistant integration

- BLE GATT communication via bleak (UART-over-GATT, service 0xff00)
- Parses 0x03 (general info) and 0x04 (cell voltages) frames
- Protocol verified against official RS485/UART spec V4
- DataUpdateCoordinator with 5s poll interval (configurable 2-60s)
- Auto-reconnect on BLE disconnect
- Config flow: BT auto-discovery + manual MAC entry + options flow
- Sensors: voltage, current, power, SoC, capacity, cycles, temps, cells, cell delta
- HACS-ready (hacs.json, manifest.json)

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

custom_components/xiaoxiang_bms/manifest.json

@@ -0,0 +1,14 @@
+{
+  "domain": "xiaoxiang_bms",
+  "name": "Xiaoxiang Smart BMS",
+  "version": "1.0.0",
+  "config_flow": true,
+  "dependencies": ["bluetooth"],
+  "bluetooth": [
+    {"service_uuid": "0000ff00-0000-1000-8000-00805f9b34fb"}
+  ],
+  "requirements": [],
+  "codeowners": [],
+  "iot_class": "local_polling",
+  "documentation": "https://github.com/Jnnshschl/AndroidBMSApp"
+}