fix: various inline style cleanup, a11y improvements, and bind_param bug

- Replace style="text-align:center" with .lt-text-center utility class in
  WorkflowDesignerView, CustomFieldsView, error_403, error_404, DashboardView JS string
- Replace style="margin-top:..." with .lt-mt-sm utility in WorkflowDesignerView
- Switch comment-edit-raw data-store textareas to .is-hidden class (TicketView PHP
  + JS-rendered; ticket.js template literal) — these are never shown, only read via .value
- Add aria-describedby="visibilityGroupsHint" + id on hint <p> in CreateTicketView
- Fix bind_param type string bug in manage_workflows.php PUT handler: 'ssiiiii' → 'ssiiii'
  (7 type chars for 6 params caused binding error on workflow transition updates)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

views/admin/CustomFieldsView.php

@@ -50,7 +50,7 @@ include __DIR__ . '/../../views/layout_header.php';
               <td data-label="Label"><strong><?= htmlspecialchars($field['field_label']) ?></strong></td>
               <td data-label="Type" class="lt-text-xs"><?= ucfirst($field['field_type']) ?></td>
               <td data-label="Category" class="lt-text-xs"><?= htmlspecialchars($field['category'] ?? 'All') ?></td>
-              <td data-label="Required" style="text-align:center">
+              <td data-label="Required" class="lt-text-center">
                 <?= $field['is_required'] ? '<span class="lt-text-amber">✓</span>' : '<span class="lt-text-muted">—</span>' ?>
               </td>
               <td data-label="Status">