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>

Sources/DuooomiBleSDK/Services/AniConverter.swift

@@ -10,7 +10,7 @@ final class AniConverter {
     private let config: DuooomiBleConfig
 
     private var endpoint: URL {
-        config.apiHost.appendingPathComponent("api/auth/loomart/file/convert-to-ani")
+        URL(string: "\(config.apiHost)/api/auth/loomart/file/convert-to-ani")!
     }
 
     private let session: URLSession = {
@@ -26,15 +26,23 @@ final class AniConverter {
     }
 
     /// 调用 ANI 转换接口，返回 ani 文件的 CDN URL。
-    func convert(fileUrl: String) async throws -> String {
-        do {
-            return try await performConvert(fileUrl: fileUrl)
-        } catch let error as NSError where error.code == NSURLErrorNetworkConnectionLost {
-            return try await performConvert(fileUrl: fileUrl)
+    func convert(fileUrl: String, completion: @escaping (Result<String, Error>) -> Void) {
+        performConvert(fileUrl: fileUrl) { result in
+            switch result {
+            case .success:
+                completion(result)
+            case .failure(let error):
+                // Retry once on connection lost
+                if (error as NSError).code == NSURLErrorNetworkConnectionLost {
+                    self.performConvert(fileUrl: fileUrl, completion: completion)
+                } else {
+                    completion(.failure(error))
+                }
+            }
         }
     }
 
-    private func performConvert(fileUrl: String) async throws -> String {
+    private func performConvert(fileUrl: String, completion: @escaping (Result<String, Error>) -> Void) {
         var request = URLRequest(url: endpoint)
         request.httpMethod = "POST"
         request.setValue("application/json", forHTTPHeaderField: "content-type")
@@ -47,32 +55,49 @@ final class AniConverter {
             "height": config.aniHeight,
             "fps": config.aniFps,
         ]
-        request.httpBody = try JSONSerialization.data(withJSONObject: body)
 
-        let (data, response) = try await session.data(for: request)
-
-        if let http = response as? HTTPURLResponse, !(200..<300).contains(http.statusCode) {
-            throw AniConverterError(message: "HTTP \(http.statusCode)")
+        do {
+            request.httpBody = try JSONSerialization.data(withJSONObject: body)
+        } catch {
+            completion(.failure(error))
+            return
         }
 
-        guard let json = try JSONSerialization.jsonObject(with: data) as? [String: Any] else {
-            throw AniConverterError(message: "Invalid JSON response")
-        }
+        session.dataTask(with: request) { data, response, error in
+            if let error = error {
+                completion(.failure(error))
+                return
+            }
 
-        guard (json["success"] as? Bool) == true,
-              let outer = json["data"] as? [String: Any] else {
-            throw AniConverterError(message: "ANI API reported failure")
-        }
+            if let http = response as? HTTPURLResponse, !(200..<300).contains(http.statusCode) {
+                completion(.failure(AniConverterError(message: "HTTP \(http.statusCode)")))
+                return
+            }
 
-        if (outer["status"] as? Bool) != true {
-            let msg = (outer["msg"] as? String) ?? "ANI conversion failed"
-            throw AniConverterError(message: msg)
-        }
+            guard let data = data,
+                  let json = (try? JSONSerialization.jsonObject(with: data)) as? [String: Any] else {
+                completion(.failure(AniConverterError(message: "Invalid JSON response")))
+                return
+            }
 
-        guard let aniUrl = outer["data"] as? String, !aniUrl.isEmpty else {
-            throw AniConverterError(message: "Missing ani url in response")
-        }
+            guard (json["success"] as? Bool) == true,
+                  let outer = json["data"] as? [String: Any] else {
+                completion(.failure(AniConverterError(message: "ANI API reported failure")))
+                return
+            }
 
-        return aniUrl
+            if (outer["status"] as? Bool) != true {
+                let msg = (outer["msg"] as? String) ?? "ANI conversion failed"
+                completion(.failure(AniConverterError(message: msg)))
+                return
+            }
+
+            guard let aniUrl = outer["data"] as? String, !aniUrl.isEmpty else {
+                completion(.failure(AniConverterError(message: "Missing ani url in response")))
+                return
+            }
+
+            completion(.success(aniUrl))
+        }.resume()
     }
 }