fix: Keep webxdc instance for delete_device_after period after a status update (#5365)

If `delete_device_after` is configured, that period should be counted for webxdc instances from the
last status update, otherwise nothing prevents from deleting them. Use `msgs.timestamp_rcvd` to
store the last status update timestamp, it anyway isn't used for anything except displaying a
detailed message info. Also, as `ephemeral::select_expired_messages()` now also checks
`timestamp_rcvd`, we have an improvement that a message is guaranteed not to be deleted for the
`delete_device_after` period since its receipt. Before only the sort timestamp was checked which is
derived from the "sent" timestamp.

src/ephemeral.rs

@@ -392,7 +392,8 @@ WHERE
 SELECT id, chat_id, type
 FROM msgs
 WHERE
-  timestamp < ?
+  timestamp < ?1
+  AND timestamp_rcvd < ?1
   AND chat_id > ?
   AND chat_id != ?
   AND chat_id != ?
@@ -490,7 +491,7 @@ async fn next_delete_device_after_timestamp(context: &Context) -> Result<Option<
             .sql
             .query_get_value(
                 r#"
-                SELECT min(timestamp)
+                SELECT min(max(timestamp, timestamp_rcvd))
                 FROM msgs
                 WHERE chat_id > ?
                   AND chat_id != ?