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/Settings/PlayerControls/ButtonConfigurationView.swift

@@ -72,6 +72,7 @@ struct ButtonConfigurationView: View {
                 String(localized: "settings.playerControls.buttonNotFound"),
                 systemImage: "exclamationmark.triangle"
             )
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
         }
     }
 

Yattee/Views/Settings/PlayerControls/MiniPlayerEditorView.swift

@@ -283,6 +283,7 @@ struct MiniPlayerButtonConfigurationView: View {
                 String(localized: "settings.playerControls.buttonNotFound"),
                 systemImage: "exclamationmark.triangle"
             )
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
         }
     }
 

Yattee/Views/Settings/PlayerControls/PillButtonConfigurationView.swift

@@ -41,6 +41,7 @@ struct PillButtonConfigurationView: View {
                 String(localized: "settings.playerControls.buttonNotFound"),
                 systemImage: "exclamationmark.triangle"
             )
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
         }
     }