feat: 重写 SDK 支持 iOS 12.2，移除 async/await 和 Combine

- 所有公开 API 改为 completion handler (Result<T, Error>)
- 状态通知改为 DuooomiBleSDKDelegate 协议
- 移除 Sendable、@MainActor、AsyncStream、CheckedContinuation
- 网络请求改为 URLSession.dataTask 回调
- BLE 通信改为 delegate + 闭包模式
- deployment target 降至 iOS 12.2

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Podfile.lock

@@ -0,0 +1,16 @@
+PODS:
+  - DuooomiBleSDK (0.1.0)
+
+DEPENDENCIES:
+  - DuooomiBleSDK (from `./`)
+
+EXTERNAL SOURCES:
+  DuooomiBleSDK:
+    :path: "./"
+
+SPEC CHECKSUMS:
+  DuooomiBleSDK: e80989b9a674116a25ef59b3ddfa3edabccfba6f
+
+PODFILE CHECKSUM: aa25954b2fc8a5cf1a3f6b2eaa0d37f103cc9b81
+
+COCOAPODS: 1.16.2