web: migrate health notifications to js_interop; add browser hook

- Replace dart:js with package:js in health_check_service_web.dart\n- Implement showHealthCheckNotification in web/index.html\n- Pin js dependency to ^0.6.7 for flutter_secure_storage_web compatibility

auth: harden AuthInterceptor + tests

- Allow overrideAuthRepository injection for testing\n- Normalize imports to package: paths\n- Add unit test covering token attach, 401→refresh→retry, and failure path\n- Add integration test skeleton gated by env vars

ui/data: map User.companyName to list column

- Add companyName to domain User\n- Map UserDto.company?.name\n- Render companyName in user_list

cleanup: remove legacy equipment table + unused code; minor warnings

- Remove _buildFlexibleTable and unused helpers\n- Remove unused zipcode details and cache retry constant\n- Fix null-aware and non-null assertions\n- Address child-last warnings in administrator dialog

docs: update AGENTS.md session context

lib/screens/equipment/equipment_in_form.dart

@@ -233,13 +233,13 @@ class _EquipmentInFormScreenState extends State<EquipmentInFormScreen> {
               label: Text(_controller.isFieldReadOnly('serialNumber') 
                   ? '장비 번호 * 🔒' : '장비 번호 *'),
               validator: (value) {
-                if (value?.trim().isEmpty ?? true) {
+                if ((value ?? '').trim().isEmpty) {
                   return '장비 번호는 필수입니다';
                 }
                 return null;
               },
               onChanged: _controller.isFieldReadOnly('serialNumber') ? null : (value) {
-                _controller.serialNumber = value?.trim() ?? '';
+                _controller.serialNumber = value.trim();
                 setState(() {});
                 print('DEBUG [장비번호 입력] value: "$value", controller.serialNumber: "${_controller.serialNumber}"');
               },
@@ -252,7 +252,7 @@ class _EquipmentInFormScreenState extends State<EquipmentInFormScreen> {
               placeholder: const Text('바코드를 입력하세요'),
               label: const Text('바코드'),
               onChanged: (value) {
-                _controller.barcode = value?.trim() ?? '';
+                _controller.barcode = value.trim();
                 print('DEBUG [바코드 입력] value: "$value", controller.barcode: "${_controller.barcode}"');
               },
             ),
@@ -504,7 +504,7 @@ class _EquipmentInFormScreenState extends State<EquipmentInFormScreen> {
               label: const Text('워런티 번호 *'),
               placeholder: const Text('워런티 번호를 입력하세요'),
               validator: (value) {
-                if (value.trim().isEmpty ?? true) {
+                if (value.trim().isEmpty) {
                   return '워런티 번호는 필수입니다';
                 }
                 return null;
@@ -683,4 +683,4 @@ class _EquipmentInFormScreenState extends State<EquipmentInFormScreen> {
     ];
   }
 
-}
+}