PARIS, June 26 (Reuters) - European stocks were seen flat to slightly higher on Tuesday, halting their sharp three-session sell-off, but doubts about whether this week's EU summit will lead to significant measures to shore up the region's most indebted countries could limit the rebound. Also rattling investors, Cyprus said late on Monday it was applying to Brussels for a bailout, both for its banking sector, hit by exposure to Greece, and for its budget deficit. Moody's Investors Servic