Bidirectional progress sync, reliable background history, MB-accurate download ring

- Bidirectional progress sync: server's `lastUpdate` now parsed correctly; pull
  timer (60s) + scenePhase hook reconcile against local state. Server-newer
  while paused/playing stashes a `pendingServerProgress` and surfaces a prompt
  on next Play; server-older triggers an immediate push.
- History: lockscreen/Control-Center skip & scrub now route through AppState
  via `onRemoteSkip`/`onRemoteSeek` callbacks (previously bypassed history).
  `AppState.skip(by:)` itself now records the pre-skip position.
- Chapter detection moved to the AVPlayer periodic time observer — fires
  reliably while the app is backgrounded or the device is locked, where the
  5s runloop Timer can be throttled.
- Always fetch item detail when online (even for downloaded items) so
  `item.chapters` is populated and history entries get chapter titles.
- DownloadManager: per-track byte-fraction progress, so single-track 1+GB
  audiobooks' ring grows smoothly instead of staying at 0% until done.
- PlayerBar: extracted ScrubberView into its own struct so per-second time
  updates no longer re-render the parent (fixes iOS history-popup flicker).
- App icon: re-embedded sRGB profile in marketing icon; bumped version 2.0
  to 2.1.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ABS Client/Audiobookshelf swift/Services/ABSClient.swift

@@ -167,10 +167,15 @@ final class ABSClient {
             currentTime: dto.currentTime ?? 0,
             duration: dto.duration ?? 0,
             isFinished: dto.isFinished ?? false,
-            updatedAt: Date()
+            updatedAt: Self.parseLastUpdate(dto.lastUpdate)
         )
     }
 
+    private static func parseLastUpdate(_ ms: Double?) -> Date {
+        guard let ms, ms > 0 else { return Date() }
+        return Date(timeIntervalSince1970: ms / 1000)
+    }
+
     func saveProgress(_ progress: PlaybackProgress) async throws {
         let body: [String: Any] = [
             "currentTime": progress.currentTime,
@@ -200,7 +205,7 @@ final class ABSClient {
                 currentTime: p.currentTime ?? 0,
                 duration: p.duration ?? 0,
                 isFinished: p.isFinished ?? false,
-                updatedAt: Date()
+                updatedAt: Self.parseLastUpdate(p.lastUpdate)
             )
         }
     }