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/Models/AppModel.swift

@@ -251,6 +251,16 @@ final class AppModel: ObservableObject {
         )
     }
 
+    /// Aggregated call history for the «Звонки» tab, newest first.
+    var callHistoryMessages: [ChatMessage] {
+        messages
+            .filter { $0.callHistory != nil }
+            .sorted { lhs, rhs in
+                if lhs.timestamp != rhs.timestamp { return lhs.timestamp > rhs.timestamp }
+                return lhs.clientID < rhs.clientID
+            }
+    }
+
     var selectedMessages: [ChatMessage] {
         guard let selectedConversationID else { return [] }
         if selectedMessagesCacheConversationID == selectedConversationID {