fix: 阻塞调用包裹 withContext(IO) 使 withTimeout 可正确中断

- 步骤1 wifiDirect.initialize() 是同步阻塞调用，withTimeout 无法中断
- 改为 withTimeout(5000L) { withContext(Dispatchers.IO) { ... } }
- 超时后协程在 IO 线程被取消，TimeoutCancellationException 正确到达 catch
- 步骤2-5 同样加 withContext 防御性包裹

app/src/main/java/com/qwenpaw/miracast/AirDisplayManager.kt

@@ -218,13 +218,15 @@ class AirDisplayManager(private val context: Context) {
         _uiState.update { it.copy(serviceState = ServiceState.Initializing) }
 
         try {
-            // 1. Wi-Fi Direct
+            // 1. Wi-Fi Direct（阻塞调用，用 withContext+withTimeout 可正确中断）
             Log.w(TAG, "  步骤1: wifiDirect.initialize()")
             try {
-                withTimeout(5000L) { wifiDirect.initialize() }
+                withTimeout(5000L) {
+                    withContext(Dispatchers.IO) { wifiDirect.initialize() }
+                }
                 Log.w(TAG, "  步骤1: 完成")
             } catch (e: TimeoutCancellationException) {
-                Log.w(TAG, "  步骤1: 超时（5秒）")
+                Log.w(TAG, "  步骤1: 超时（5秒），Wi-Fi Direct 不可用")
             } catch (e: Exception) {
                 Log.w(TAG, "  步骤1: 失败（非致命）: ${e.message}")
             }
@@ -232,7 +234,7 @@ class AirDisplayManager(private val context: Context) {
             // 2. 启动 ADP
             Log.w(TAG, "  步骤2: adp.start()")
             try {
-                withTimeout(5000L) { adp.start(AirDisplayProtocol.DEFAULT_PORT) }
+                withTimeout(5000L) { withContext(Dispatchers.IO) { adp.start(AirDisplayProtocol.DEFAULT_PORT) } }
                 Log.w(TAG, "  步骤2: 完成")
             } catch (e: TimeoutCancellationException) {
                 Log.w(TAG, "  步骤2: 超时（5秒）")
@@ -243,7 +245,7 @@ class AirDisplayManager(private val context: Context) {
             // 3. 注册 mDNS
             Log.w(TAG, "  步骤3: mdns.register()")
             try {
-                withTimeout(3000L) { mdns.register() }
+                withTimeout(3000L) { withContext(Dispatchers.IO) { mdns.register() } }
                 Log.w(TAG, "  步骤3: 完成")
             } catch (e: TimeoutCancellationException) {
                 Log.w(TAG, "  步骤3: 超时（3秒）")
@@ -254,7 +256,7 @@ class AirDisplayManager(private val context: Context) {
             // 4. 启动 RTSP
             Log.w(TAG, "  步骤4: rtsp.start()")
             try {
-                withTimeout(5000L) { rtsp.start() }
+                withTimeout(5000L) { withContext(Dispatchers.IO) { rtsp.start() } }
                 Log.w(TAG, "  步骤4: 完成")
             } catch (e: TimeoutCancellationException) {
                 Log.w(TAG, "  步骤4: 超时（5秒）")
@@ -265,7 +267,7 @@ class AirDisplayManager(private val context: Context) {
             // 5. 发现设备
             Log.w(TAG, "  步骤5: wifiDirect.startDiscovery()")
             try {
-                withTimeout(3000L) { wifiDirect.startDiscovery() }
+                withTimeout(3000L) { withContext(Dispatchers.IO) { wifiDirect.startDiscovery() } }
             } catch (e: TimeoutCancellationException) {
                 Log.w(TAG, "  步骤5: 超时（3秒）")
             } catch (e: Exception) {