Fix ContentUnavailableView centering on Apple TV

On tvOS, ContentUnavailableView inside a Group doesn't expand to fill
available space — it sizes to content and aligns top-leading. Add
.frame(maxWidth: .infinity, maxHeight: .infinity) to all instances
so they center correctly in their parent containers.

Yattee/Views/Video/DownloadQualitySheet.swift

@@ -415,6 +415,7 @@ struct DownloadQualitySheet: View {
             } description: {
                 Text(String(localized: "download.noStreams.description"))
             }
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
         } else {
             VStack(spacing: 0) {
                 ForEach(Array(videoStreams.enumerated()), id: \.element.url) { index, stream in
@@ -448,6 +449,7 @@ struct DownloadQualitySheet: View {
             ContentUnavailableView {
                 Label(String(localized: "download.noAudio.title"), systemImage: "speaker.slash")
             }
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
         } else {
             VStack(spacing: 0) {
                 ForEach(Array(audioStreams.enumerated()), id: \.element.url) { index, stream in

Yattee/Views/Video/PlaylistSelectorSheet.swift

@@ -74,6 +74,7 @@ struct PlaylistSelectorSheet: View {
                             } description: {
                                 Text(String(localized: "playlist.empty.description"))
                             }
+                            .frame(maxWidth: .infinity, maxHeight: .infinity)
                         }
                     }
                 }

Yattee/Views/Video/VideoInfoView.swift

@@ -532,6 +532,7 @@ struct VideoInfoView: View {
                 }
             }
         }
+        .frame(maxWidth: .infinity, maxHeight: .infinity)
     }
 
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