fix: keep chat list ordering stable on realtime updates

- preserve chat sort timestamps when realtime payloads omit timestamps

- use safe fallback timestamps for local chat list updates

android/app/src/main/java/ru/daemonlord/messenger/data/chat/local/dao/ChatDao.kt

@@ -119,8 +119,8 @@ interface ChatDao {
         UPDATE chats
         SET last_message_text = :lastMessageText,
             last_message_type = :lastMessageType,
-            last_message_created_at = :lastMessageCreatedAt,
-            updated_sort_at = :updatedSortAt
+            last_message_created_at = COALESCE(:lastMessageCreatedAt, last_message_created_at),
+            updated_sort_at = COALESCE(:updatedSortAt, updated_sort_at, last_message_created_at)
         WHERE id = :chatId
         """
     )

android/app/src/main/java/ru/daemonlord/messenger/domain/realtime/usecase/HandleRealtimeEventsUseCase.kt

@@ -49,6 +49,7 @@ class HandleRealtimeEventsUseCase @Inject constructor(
                         val activeChatId = activeChatTracker.activeChatId.value
                         val activeUserId = tokenRepository.getActiveUserId()
                         val isOwnMessage = activeUserId != null && event.senderId == activeUserId
+                        val eventTimestamp = event.createdAt ?: java.time.Instant.now().toString()
                         val myUsername = activeUserId?.let { userId ->
                             tokenRepository.getAccounts()
                                 .firstOrNull { it.userId == userId }
@@ -84,7 +85,7 @@ class HandleRealtimeEventsUseCase @Inject constructor(
                                     text = event.text,
                                     status = null,
                                     attachmentWaveformJson = null,
-                                    createdAt = event.createdAt ?: java.time.Instant.now().toString(),
+                                    createdAt = eventTimestamp,
                                     updatedAt = null,
                                 )
                             )
@@ -93,8 +94,8 @@ class HandleRealtimeEventsUseCase @Inject constructor(
                             chatId = event.chatId,
                             lastMessageText = lastMessagePreview,
                             lastMessageType = event.type,
-                            lastMessageCreatedAt = event.createdAt,
-                            updatedSortAt = event.createdAt,
+                            lastMessageCreatedAt = eventTimestamp,
+                            updatedSortAt = eventTimestamp,
                         )
                         if (activeChatId == event.chatId) {
                             chatDao.markChatRead(chatId = event.chatId)
@@ -111,17 +112,18 @@ class HandleRealtimeEventsUseCase @Inject constructor(
                     }
 
                     is RealtimeEvent.MessageUpdated -> {
+                        val updateTimestamp = event.updatedAt ?: java.time.Instant.now().toString()
                         messageDao.updateMessageText(
                             messageId = event.messageId,
                             text = event.text,
-                            updatedAt = event.updatedAt,
+                            updatedAt = updateTimestamp,
                         )
                         chatDao.updateLastMessage(
                             chatId = event.chatId,
                             lastMessageText = event.text?.takeIf { it.isNotBlank() } ?: fallbackMessagePreview(event.type),
                             lastMessageType = event.type,
-                            lastMessageCreatedAt = event.updatedAt,
-                            updatedSortAt = event.updatedAt,
+                            lastMessageCreatedAt = updateTimestamp,
+                            updatedSortAt = updateTimestamp,
                         )
                         if (activeChatTracker.activeChatId.value == event.chatId) {
                             messageRepository.syncRecentMessages(chatId = event.chatId)