polish iOS study flow

mobile/ios-app/Core/Media/PlayerCoordinator.swift

@@ -1,7 +1,37 @@
+import AVFoundation
 import Combine
 import Foundation
 
+@MainActor
 final class PlayerCoordinator: ObservableObject {
+    let player: AVPlayer
+
     @Published var isPlaying = false
     @Published var playbackPositionMs: Int = 0
+
+    init(previewURL: URL = URL(string: "https://cdn.example.com/hermes/sample-event/master.m3u8")!) {
+        self.player = AVPlayer(url: previewURL)
+        self.player.actionAtItemEnd = .pause
+    }
+
+    func prepareForPreview() {
+        player.seek(to: .zero)
+        player.play()
+        isPlaying = true
+    }
+
+    func play() {
+        player.play()
+        isPlaying = true
+    }
+
+    func pause() {
+        player.pause()
+        isPlaying = false
+    }
+
+    func restart() {
+        player.seek(to: .zero)
+        play()
+    }
 }

mobile/ios-app/Core/Media/StudyVideoPlayerView.swift

@@ -0,0 +1,18 @@
+import AVKit
+import SwiftUI
+
+struct StudyVideoPlayerView: View {
+    @ObservedObject var coordinator: PlayerCoordinator
+
+    var body: some View {
+        VideoPlayer(player: coordinator.player)
+            .frame(maxWidth: .infinity)
+            .frame(height: 224)
+            .clipShape(RoundedRectangle(cornerRadius: HermesTheme.cornerRadius, style: .continuous))
+            .overlay(
+                RoundedRectangle(cornerRadius: HermesTheme.cornerRadius, style: .continuous)
+                    .stroke(HermesTheme.accent.opacity(0.12), lineWidth: 1)
+            )
+            .background(HermesTheme.surfaceElevated)
+    }
+}