fix: iOS OOM during PiP playback cycles

Cancel leaked stream subscriptions in video player dispose and flush
sample buffer layer on PiP teardown/cleanup to release video frames.

ios/Runner/MpvPlayer/MpvPipController.swift

@@ -245,10 +245,17 @@ class MpvPipController: NSObject {
         }
         pipController = nil
         delegateHelper = nil
+        sampleBufferLayer.flushAndRemoveImage()
+        sampleBufferLayer.controlTimebase = nil
         sampleBufferLayer.removeFromSuperlayer()
         containerView?.removeFromSuperview()
         containerView = nil
     }
+
+    /// Flush enqueued sample buffers from the layer to free video frame memory
+    func flushLayer() {
+        sampleBufferLayer.flushAndRemoveImage()
+    }
 }
 
 // MARK: - PiP Delegate Helper (iOS 15+)

ios/Runner/MpvPlayer/MpvPlayerPlugin.swift

@@ -171,6 +171,7 @@ class MpvPlayerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler, MpvPlayerD
         playerCore?.isPipActive = false
         isManualPipRequest = false
         stopPipTimebaseSync()
+        pipController?.flushLayer()
         _ = playerCore?.switchToGpuNextVO()
         if pause { playerCore?.setProperty("pause", value: "yes") }
         if notify { pipChannel?.invokeMethod("onPipChanged", arguments: false) }