Apply one category to many bank transactions

Applies one account (and optional contact, tax rate, and class) to up to 200 ready or posted bank transactions. Each row uses the single-row reclassify rules: ready rows are coded but not posted, posted rows update their category line, and rows in a completed reconciliation are refused. Posted invoice or bill payments and posted rows whose other line is Accounts Receivable, Accounts Payable, or another bank or cash account are skipped (skipped: true on the result) because their category cannot change without an Undo. An omitted taxRateId, contactId, or classId keeps the row's current value; null clears it. Failures are reported per row and never stop the batch. Rule learning follows each change.