Build a draft QuickBooks import batch (#2642)

opening_balance: one balanced brought-forward entry at the cutoff from a trial balance snapshot as of the day before the cutoff; after the opening is posted, a later snapshot builds a true-up that posts only the per-account difference. activity: every postable QuickBooks object from the latest completed read dated from the cutoff through dateTo (default today) that is not already posted, each with a default decision (post, duplicate of a native bank row, skip, or blocked with a reason). Nothing posts until the batch is approved and posted.