feat(login): 添加调试模式下的测试登录功能

- 在登录界面添加了测试用户登录按钮
- 仅在DEBUG模式下显示测试登录选项
- 集成测试用户1和测试用户2的快速登录功能
- 移动IM SDK中的事件监听器定义位置以优化代码结构

sample-app/src/main/java/com/xuqm/sdk/sample/ui/auth/LoginScreen.kt

@@ -32,6 +32,7 @@ import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.lifecycle.viewmodel.initializer
 import androidx.lifecycle.viewmodel.viewModelFactory
 import com.xuqm.sdk.sample.di.AppDependencies
+import com.xuqm.sdk.sample.BuildConfig
 import android.widget.Toast
 
 @Composable
@@ -122,5 +123,15 @@ fun LoginScreen(
         TextButton(onClick = onOpenEnvironment) {
             Text("环境设置")
         }
+
+        if (BuildConfig.DEBUG) {
+            Spacer(Modifier.height(8.dp))
+            TextButton(onClick = { viewModel.login("testuser1", "test123") }) {
+                Text("[测试] 登录用户1", style = MaterialTheme.typography.bodySmall)
+            }
+            TextButton(onClick = { viewModel.login("testuser2", "test123") }) {
+                Text("[测试] 登录用户2", style = MaterialTheme.typography.bodySmall)
+            }
+        }
     }
 }

sdk-im/src/main/java/com/xuqm/sdk/im/ImSDK.kt

@@ -98,6 +98,13 @@ object ImSDK {
         fun onConversationsChanged(conversations: List<ConversationData>)
     }
 
+    private val conversationEventListener = object : ImEventListener {
+        override fun onMessage(message: ImMessage) { onMessageReceived(message) }
+        override fun onGroupMessage(message: ImMessage) { onMessageReceived(message) }
+        override fun onRead(message: ImMessage) { onReadReceived(message) }
+        override fun onRevoke(message: ImMessage) { onRevokeReceived(message) }
+    }
+
     init {
         XuqmSDK.currentLoginSession?.let { onSdkLogin(it) }
     }
@@ -901,13 +908,6 @@ object ImSDK {
         )
     }
 
-    private val conversationEventListener = object : ImEventListener {
-        override fun onMessage(message: ImMessage) { onMessageReceived(message) }
-        override fun onGroupMessage(message: ImMessage) { onMessageReceived(message) }
-        override fun onRead(message: ImMessage) { onReadReceived(message) }
-        override fun onRevoke(message: ImMessage) { onRevokeReceived(message) }
-    }
-
     private fun getConversationTargetId(message: ImMessage): String {
         return if (message.chatType.uppercase() == "GROUP") {
             message.toId