fix(iOS): 修复视频显示模式为填充

将远端视频渲染视图和内容视图的视频内容模式从 `.fit` 改为 `.fill`，并调整控制面板布局，将录制与断开按钮单独成行，提升界面利用率与操作体验。

webrtc_controller_ios/web_rtc_controller_ios/Views/ContentView.swift

@@ -156,6 +156,8 @@ private struct ControlPanelView: View {
     }
 
     private var topBar: some View {
+        VStack(spacing: 6) {
+            // 第一行：状态 + 串流模式切换 + 分辨率 + 帧率
             ScrollView(.horizontal, showsIndicators: false) {
                 HStack(spacing: 12) {
                     Text(viewModel.statusText)
@@ -213,7 +215,13 @@ private struct ControlPanelView: View {
                             .font(.footnote)
                             .fixedSize()
                     }
+                }
+                .padding(.horizontal, 12)
+                .padding(.vertical, 6)
+            }
 
+            // 第二行：录制 + 断开（当前行下方）
+            HStack(spacing: 12) {
                 // 录制远端视频（MP4）
                 Button {
                     if viewModel.isRecording {
@@ -241,9 +249,11 @@ private struct ControlPanelView: View {
                 .buttonStyle(.borderedProminent)
                 .tint(.red)
                 .controlSize(.small)
+
+                Spacer()
             }
             .padding(.horizontal, 12)
-            .padding(.vertical, 6)
+            .padding(.bottom, 6)
         }
         .background(Color(white: 0.1))
     }
@@ -269,7 +279,7 @@ private struct ControlPanelView: View {
                             viewModel.sendSwipe(x1: x1, y1: y1, x2: x2, y2: y2, duration: duration)
                         })
                 }
-                .aspectRatio(viewModel.videoAspect, contentMode: .fit)
+                .aspectRatio(viewModel.videoAspect, contentMode: .fill)
                 .frame(maxWidth: .infinity, maxHeight: .infinity)
 
                 // 录制中指示（左上角红点）

webrtc_controller_ios/web_rtc_controller_ios/Views/RemoteVideoView.swift

@@ -7,7 +7,7 @@ struct RemoteVideoView: UIViewRepresentable {
     let videoView: RTCMTLVideoView
 
     func makeUIView(context: Context) -> RTCMTLVideoView {
-        videoView.videoContentMode = .scaleAspectFit
+        videoView.videoContentMode = .scaleAspectFill
         return videoView
     }