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>

Tests/DuooomiBleSDKTests/PlayModeTests.swift

@@ -88,7 +88,7 @@ final class BindPayloadEncodingTests: XCTestCase {
 
 final class SetPlayModeGuardTests: XCTestCase {
     private func makeSDK() -> DuooomiBleSDK {
-        DuooomiBleSDK(config: DuooomiBleConfig(apiKey: "test", owner: "test-owner", scanNamePrefix: "Duooomi-"))
+        DuooomiBleSDK(config: DuooomiBleConfig(apiKey: "test", brand: "test-brand", scanNamePrefix: "Duooomi-"))
     }
 
     func testSetPlayModeFailsWhenNotConnected() {