Improve tvOS settings layout: use navigation instead of sheets, fix focus clipping

- Replace sheets with navigationDestination for Add/Edit Source on tvOS
  (tvOS sheets have fixed size that doesn't fit the content)
- Fix focused cell clipping by replacing TVSettingsContainer's frame-based
  layout with safeAreaInset, matching the main settings view pattern
- Use standard List with .listStyle(.grouped) for Sources on tvOS
- Add sidebar icons and titles to TVSettingsContainer for all settings
  subviews, utilizing the left column space
- Remove redundant large navigation titles on tvOS (shown in sidebar)
- Move Edit Source Save button from toolbar into form above Delete button
  for better tvOS focus navigation

Yattee/Views/Settings/LayoutNavigationSettingsView.swift

@@ -30,7 +30,9 @@ struct LayoutNavigationSettingsView: View {
                 HandoffSection(settings: settings)
             }
         }
+        #if !os(tvOS)
         .navigationTitle(String(localized: "settings.layoutNavigation.title"))
+        #endif
         #if os(iOS)
         .navigationBarTitleDisplayMode(.inline)
         #endif