Fix tvOS legacy import rows acting as a single Remove button

On tvOS a Form row is one focusable unit, so the legacy account/source
cards - header, credential fields, and both buttons stacked in a single
row - focused as a whole and every click fired the first button (Remove),
making credentials and Import unreachable.

- Split the tvOS rows into individually focusable rows (info header,
  fields, Import, Remove), keeping the card layout on iOS/macOS
- Wrap the tvOS entry points in TVSidebarDetailContainer and drop the
  tvOS navigationTitle that rendered as a ghost behind the form
- Present the review screen from the first-launch alert as a
  fullScreenCover on tvOS: sheets render as a small transparent card
  that cannot fit the sidebar layout (Menu button dismisses the cover)
- Dim disabled TVSettingsButtonStyle buttons
- Widen the row icon frame for tvOS glyph sizes and skip the caption
  when it would repeat the host shown as the title

Yattee/Views/Settings/AdvancedSettingsView.swift

@@ -412,7 +412,12 @@ struct AdvancedSettingsView: View {
             if appEnvironment?.legacyMigrationService.hasLegacyDataToImport() == true {
                 #if os(tvOS)
                 NavigationLink {
-                    LegacyDataImportView()
+                    TVSidebarDetailContainer(
+                        systemImage: "person.badge.key",
+                        title: String(localized: "migration.accounts.title")
+                    ) {
+                        LegacyDataImportView()
+                    }
                 } label: {
                     Label(String(localized: "migration.accounts.title"), systemImage: "person.badge.key")
                 }