Fix layout regressions, nav drawer structure, and security issues

- base.css: add width:100%+min-width:0 to .lt-main so flex column body
  doesn't shrink content due to margin:0 auto from .lt-container
- layout_header.php: restructure mobile nav drawer to match web_template
  exactly (nav-drawer-links nav, direct <a> links, section div, no ul/li
  wrapper, overlay after drawer); fix lt-nav-overlay id mismatch with
  base.js; rename lt-header-username -> lt-header-user (matches CSS);
  add JSON_HEX_TAG to all inline json_encode calls (closes </script> XSS)
- base.css: add lt-kv-row/label/value aliases (display:contents pattern
  used in web_template v1.2 kv-grid); add lt-badge-sm variant
- Admin views: add missing .catch() on editField/editRecurring/loadUsers;
  add JSON_HEX_TAG to json_encode in TemplatesView/WorkflowDesignerView
- TicketView: add JSON_HEX_TAG to all ticket-data json_encode calls

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

views/admin/CustomFieldsView.php

@@ -202,8 +202,10 @@ function editField(id) {
                 }
                 document.getElementById('cfModalTitle').textContent = 'Edit Custom Field';
                 lt.modal.open('fieldModal');
+            } else {
+                lt.toast.error(data.error || 'Failed to load field');
             }
-        });
+        }).catch(function () { lt.toast.error('Failed to load field'); });
 }
 
 function deleteField(id) {