feat(sdk): 重命名 owner→brand 并在硬绑前校验设备品牌

- DuooomiBleConfig.owner → brand（语义：设备品牌名），HTTP header x-owner 不变
- bind() 前置 verifyBrand：缺 deviceInfo 先 getDeviceInfo，与 config.brand 严格匹配，不一致主动断连并抛 .brandMismatch
- README 抹除软绑/对账/UpgradeRecord 等内部实现细节，仅保留厂商面向的公开 API（功能代码完全保留）

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Sources/DuooomiBleSDK/DuooomiBleSDK.swift

@@ -118,7 +118,7 @@ public final class DuooomiBleSDK: NSObject {
         super.init()
 
         protocolService.delegate = self
-        BleLog.i("SDK initialized (apiHost=\(config.apiHost), owner=\(config.owner))", "SDK")
+        BleLog.i("SDK initialized (apiHost=\(config.apiHost), brand=\(config.brand))", "SDK")
         setupDisconnectHandler()
 
         // UpgradeRecord 变化（含对账上报结果）→ delegate 通知