Unstick more tvOS focus dead-ends in channel views

Settings → Notifications → Manage Channels: wrap the tvOS NavigationLink
destination in TVSidebarDetailContainer(showsDismissButton: true) so the
no-subscriptions, error, and loading states all have a focusable Done.

Channels sidebar tab: lift the tvOS search field + View Options button
out of the loaded-channels branch and render it above every state. The
empty state previously had zero focusable elements, leaving the right
pane blank when swiping in from the sidebar.

Yattee/Views/Settings/NotificationSettingsView.swift

@@ -137,7 +137,13 @@ private struct ManageChannelsSection: View {
         SettingsFormSection {
             #if os(tvOS)
             NavigationLink {
-                ManageChannelNotificationsView()
+                TVSidebarDetailContainer(
+                    systemImage: "bell.badge",
+                    title: String(localized: "settings.notifications.manageChannels"),
+                    showsDismissButton: true
+                ) {
+                    ManageChannelNotificationsView()
+                }
             } label: {
                 Label(
                     String(localized: "settings.notifications.manageChannels"),