feat: 集成 Jetpack Compose UI 并重构配置界面

- 添加 Jetpack Compose 依赖和编译器插件
- 重构 MainActivity 为 Compose UI 实现
- 新增配置界面，支持服务器地址输入和保存
- 添加开始/停止推流控制按钮
- 改进 WebRTC 客户端生命周期管理

app/build.gradle

@@ -1,5 +1,6 @@
 plugins {
     alias(libs.plugins.android.application)
+    alias(libs.plugins.compose.compiler)
 }
 
 android {
@@ -26,9 +27,21 @@ android {
         sourceCompatibility JavaVersion.VERSION_11
         targetCompatibility JavaVersion.VERSION_11
     }
+    buildFeatures {
+        compose true
+    }
 }
 
 dependencies {
+    implementation libs.androidx.core.ktx
+    implementation libs.androidx.lifecycle.runtime.ktx
+    implementation libs.androidx.activity.compose
+    implementation platform(libs.androidx.compose.bom)
+    implementation libs.androidx.compose.ui
+    implementation libs.androidx.compose.ui.graphics
+    implementation libs.androidx.compose.ui.tooling.preview
+    implementation libs.androidx.compose.material3
+
     implementation libs.appcompat
     implementation libs.material
     testImplementation libs.junit