Corrections/reversals logged separately with approval chain

When a financial correction or reversal is handled by deleting or modifying the original log record, the audit trail loses continuity — an examiner reviewing the log will see the final state but not the error and its correction, which is exactly the information they need to evaluate whether the process is operating with integrity. SOX §404 requires that corrections to financial records follow a controlled, documented process. NIST 800-53 AU-10 (Non-Repudiation) requires that the organization protect against individuals falsely denying having performed particular actions — an undocumented reversal creates the ability to deny that an original transaction ever occurred. FINRA Rule 4511 requires that corrections be documented as corrections, not as silent replacements. CWE-284 (Improper Access Control) covers the case where any operator can issue a reversal without a separate approver checking the request.

Implement corrections as a two-record pattern in src/services/corrections.ts: one record for the approval event, one for the reversal transaction, neither touching the original row:

async function approveAndReverseTransaction(
  correctionId: string, approverUserId: string
) {
  const correction = await db('corrections').where({ id: correctionId }).first();
  await db('transaction_logs').insert([
    {
      user_id: approverUserId,
      operation_type: 'correction_approved',
      details: JSON.stringify({
        correction_id:          correctionId,
        original_transaction_id: correction.original_transaction_id,
        reason:                 correction.reason,
        requested_by:           correction.requested_by
      }),
      timestamp: new Date().toISOString()
    },
    {
      user_id: approverUserId,
      operation_type: 'reversal',
      details: JSON.stringify({
        original_transaction_id: correction.original_transaction_id,
        approved_by:            approverUserId,
        approved_at:            new Date().toISOString()
      }),
      timestamp: new Date().toISOString()
    }
  ]);
}

Verify requester_id !== approver_id before calling this function — a single person should never be able to self-approve a correction.