Add chapters, history, bookmarks, live download progress, and i18n

- Chapter navigation with auto-scroll to current chapter and end-of-chapter sleep timer
- Opt-in listening history (local-only) with XML export and per-item quick menu
- Bookmarks with server sync via Audiobookshelf API
- Live MB counter during downloads via URLSessionDownloadTask delegate
- In-progress downloads shown in "Heruntergeladen" with dimmed cover + ring overlay
- Cover image cache (50 MB memory / 500 MB disk URLCache)
- German/English localization (de.lproj, en.lproj)
- Loading spinner now triggers immediately on view switch instead of waiting for the network

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ABS Client/Audiobookshelf swift/Views/LibraryItemCell.swift

@@ -3,13 +3,22 @@ import SwiftUI
 struct LibraryItemCell: View {
     @Environment(AppState.self) private var app
     let item: LibraryItem
+    var dimDownloading: Bool = false
 
     var body: some View {
         VStack(alignment: .leading, spacing: 2) {
             ZStack(alignment: .bottom) {
                 ZStack(alignment: .topTrailing) {
                     cover
-                    downloadBadge.padding(4)
+                        .opacity(dimDownloading && isActivelyDownloading ? 0.55 : 1.0)
+                    if !(dimDownloading && isActivelyDownloading) {
+                        downloadBadge.padding(4)
+                    }
+                }
+                .overlay {
+                    if dimDownloading, case .downloading(let p) = app.downloads.state(for: item.downloadKey) {
+                        LargeDownloadOverlay(progress: p)
+                    }
                 }
                 CoverProgressBar(fraction: app.progressFraction(itemId: item.id, episodeId: item.episodeId))
                     .padding(.horizontal, 3)
@@ -23,16 +32,38 @@ struct LibraryItemCell: View {
                 #endif
                 .lineLimit(2)
                 .multilineTextAlignment(.leading)
-            Text(item.author)
-                .font(.system(size: 9))
-                .foregroundStyle(.secondary)
-                .lineLimit(1)
+                .opacity(dimDownloading && isActivelyDownloading ? 0.55 : 1.0)
+            HStack(spacing: 4) {
+                Text(item.author)
+                    .font(.system(size: 9))
+                    .foregroundStyle(.secondary)
+                    .lineLimit(1)
+                if dimDownloading {
+                    let bytes = app.downloads.downloadedBytes(for: item.downloadKey)
+                    if bytes > 0 {
+                        Text("·")
+                            .font(.system(size: 9))
+                            .foregroundStyle(.secondary)
+                        Text(formatBytes(bytes))
+                            .font(.system(size: 9, weight: .medium).monospacedDigit())
+                            .foregroundStyle(.secondary)
+                            .lineLimit(1)
+                            .fixedSize()
+                    }
+                }
+            }
+            .opacity(dimDownloading && isActivelyDownloading ? 0.55 : 1.0)
         }
         // Ensure the cell fills its full grid column width
         .frame(maxWidth: .infinity, alignment: .leading)
         .contextMenu { downloadMenuItems }
     }
 
+    private var isActivelyDownloading: Bool {
+        if case .downloading = app.downloads.state(for: item.downloadKey) { return true }
+        return false
+    }
+
     // MARK: - Cover
 
     private var cover: some View {
@@ -198,3 +229,40 @@ struct DownloadProgressRing: View {
         .shadow(color: .black.opacity(0.4), radius: 3, x: 0, y: 1)
     }
 }
+
+struct LargeDownloadOverlay: View {
+    let progress: Double
+    var size: CGFloat = 64
+
+    private var lineWidth: CGFloat { size / 13 }
+    private var padding: CGFloat  { size / 7  }
+    private var fontSize: CGFloat { max(9, size / 5) }
+
+    var body: some View {
+        ZStack {
+            Circle()
+                .fill(Color.black.opacity(0.65))
+            Circle()
+                .stroke(Color.white.opacity(0.2), lineWidth: lineWidth)
+                .padding(padding)
+            Circle()
+                .trim(from: 0, to: max(0.03, min(progress, 1)))
+                .stroke(Color.accentColor, style: StrokeStyle(lineWidth: lineWidth, lineCap: .round))
+                .rotationEffect(.degrees(-90))
+                .padding(padding)
+                .animation(.easeInOut(duration: 0.3), value: progress)
+            Text("\(Int(progress * 100))%")
+                .font(.system(size: fontSize, weight: .semibold).monospacedDigit())
+                .foregroundStyle(.white)
+        }
+        .frame(width: size, height: size)
+        .shadow(color: .black.opacity(0.45), radius: 6)
+    }
+}
+
+func formatBytes(_ bytes: Int64) -> String {
+    let mb = Double(bytes) / 1_048_576
+    if mb >= 1024 { return String(format: "%.1f GB", mb / 1024) }
+    if mb >= 1    { return String(format: "%.0f MB", mb) }
+    return String(format: "%.0f KB", Double(bytes) / 1024)
+}