No miracles are required for someone to be a saint - not in Scripture.
Scripture says that all regenerate Christians are Saints.
True. If the church declares someone a saint (that is, they declare that soul is in Heaven), then evidence is sought after. Miracles, performed by God, are assumed to be indicative of the soul being in Heaven, because God would not “smile upon” a soul not in Heaven with His Presence. God would not lead people astray.