add a telegram-style bottom tab bar to the main screen

- Replace the sidebar-based MainChatView with MainTabView: a custom
  bottom bar with Контакты / Звонки / Чаты / Настройки that looks the
  same on iOS and macOS, and open chats via push navigation.
- Put the search field above the chat and contact lists (searchable on
  iOS, an inline field on macOS) and add an aggregated call-history
  screen backed by model.callHistoryMessages.
- Embed SettingsView as a tab, update verify.sh guards, and keep CI on
  deterministic unit tests while the UI tests stay runnable manually.

Sources/Shared/UI/RootView.swift

@@ -16,7 +16,7 @@ struct RootView: View {
                     if model.account == nil {
                         LoginView(model: model)
                     } else {
-                        MainChatView(model: model)
+                        MainTabView(model: model)
                             .environment(\.modelContext, model.modelContext)
                     }
                 }