fix: 修复 MjpegServer.ClientHandler.isAlive 方法名冲突

重命名为 isClientAlive 以避免与 Thread.isAlive() 冲突

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

android-app/app/src/main/java/com/usbwebcam/MjpegServer.kt

@@ -60,7 +60,7 @@ class MjpegServer(private val port: Int) {
         val iterator = clients.iterator()
         while (iterator.hasNext()) {
             val handler = iterator.next()
-            if (handler.isAlive()) {
+            if (handler.isClientAlive()) {
                 handler.sendFrame(frame)
             } else {
                 iterator.remove()
@@ -144,7 +144,7 @@ class MjpegServer(private val port: Int) {
             }
         }
 
-        fun isAlive(): Boolean {
+        fun isClientAlive(): Boolean {
             return !socket.isClosed && socket.isConnected
         }
     }