core: support files folder for mobile, delete files, chat item in CRRcvFileComplete (#530)

src/Simplex/Chat/Mobile.hs

@@ -2,6 +2,7 @@
 {-# LANGUAGE DuplicateRecordFields #-}
 {-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 
 module Simplex.Chat.Mobile where
 
@@ -48,7 +49,7 @@ cChatRecvMsg cc = deRefStablePtr cc >>= chatRecvMsg >>= newCAString
 mobileChatOpts :: ChatOpts
 mobileChatOpts =
   ChatOpts
-    { dbFilePrefix = "simplex_v1", -- two database files will be created: simplex_v1_chat.db and simplex_v1_agent.db
+    { dbFilePrefix = undefined,
       smpServers = [],
       logConnections = False,
       logAgent = False,