fix(instanda): rate limiting, UTC timestamps, and close silent-failure paths

- F-06: throttle the public create per IP (20/h) and per email (5/h) before the
  paid API call and the PII write.
- F-11: wrap the create path in try/catch - on an unexpected error fail closed for
  that submission (no quote-less entry), alert admins, keep the form working.
- F-14: abort the StartQuote when the write-ahead insert fails (no unaudited call);
  fire the failure alert even when storage is disabled (build an in-memory tx).
- F-10/F-17: treat a 2xx with a missing/empty quoteRef as ambiguous
  (possible_duplicate=1), not a hard failure - a quote may exist.
- F-07: write created_at/delivered_at/event timestamps in UTC to match the gmdate()
  retention/dedupe cutoffs; display in site-local via get_date_from_gmt.
- F-09: log (no silent return) when async record_feed_result cannot resolve a
  delivered transaction.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

wp-content/plugins/esp-instanda-integration/includes/class-transactions-table.php

@@ -83,7 +83,7 @@ final class Transactions_List_Table extends \WP_List_Table {
 
     protected function column_default($item, $column_name): string {
         return match ($column_name) {
-            'submitted'   => esc_html($item->created_at) . '<br><span class="mono">#' . $item->id . '</span>',
+            'submitted'   => esc_html(get_date_from_gmt($item->created_at, 'Y-m-d H:i')) . '<br><span class="mono">#' . $item->id . '</span>',
             'email'       => esc_html($item->customer_email),
             'role'        => esc_html($item->role_label),
             'status'      => $this->status_badge($item),