ui: show XFTP servers used for a file in message info (#7088)

Surface the XFTP servers that hosted a file's chunks in the message info
screen (Android, desktop, iOS), so a user can see which servers they are
downloading from (or, for sent files, uploading to) whenever they want to know.

APIGetChatItemInfo now returns fileXftpServers, derived from the stored file
description (private snd descr for sent items, rcv descr for received items);
extraction is best-effort and never fails the call.

src/Simplex/Chat/Store/Files.hs

@@ -20,6 +20,7 @@ module Simplex.Chat.Store.Files
     createSndFileTransferXFTP,
     createSndFTDescrXFTP,
     setSndFTPrivateSndDescr,
+    getSndFTPrivateSndDescr,
     updateSndFTDescrXFTP,
     createExtraSndFTDescrs,
     updateSndFTDeliveryXFTP,
@@ -210,6 +211,15 @@ setSndFTPrivateSndDescr db User {userId} fileId sfdText = do
     "UPDATE files SET private_snd_file_descr = ?, updated_at = ? WHERE user_id = ? AND file_id = ?"
     (sfdText, currentTs, userId, fileId)
 
+getSndFTPrivateSndDescr :: DB.Connection -> User -> FileTransferId -> IO (Maybe Text)
+getSndFTPrivateSndDescr db User {userId} fileId =
+  fmap (maybe Nothing fromOnly) $
+    maybeFirstRow id $
+      DB.query
+        db
+        "SELECT private_snd_file_descr FROM files WHERE user_id = ? AND file_id = ?"
+        (userId, fileId)
+
 updateSndFTDescrXFTP :: DB.Connection -> User -> SndFileTransfer -> Text -> IO ()
 updateSndFTDescrXFTP db user@User {userId} sft@SndFileTransfer {fileId, fileDescrId} rfdText = do
   currentTs <- getCurrentTime