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/Views/ContentView.swift

@@ -2,6 +2,7 @@ import SwiftUI
 
 struct ContentView: View {
     @Environment(AppState.self) private var app
+    @Environment(\.scenePhase) private var scenePhase
     #if os(iOS)
     @State private var splashVisible = true
     #endif
@@ -18,6 +19,9 @@ struct ContentView: View {
             #endif
         }
         .task { await boot() }
+        .onChange(of: scenePhase) { _, newPhase in
+            if newPhase == .active { app.onScenePhaseActive() }
+        }
     }
 
     @ViewBuilder