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/services/inventory_history_service.dart

@@ -180,8 +180,8 @@ class InventoryHistoryService {
 
   /// 시리얼번호 결정 로직
   String _determineSerialNumber(EquipmentDto? equipment, EquipmentHistoryDto history) {
-    if (equipment != null && equipment.serialNumber != null) {
-      return equipment.serialNumber!;
+    if (equipment != null) {
+      return equipment.serialNumber;
     }
     
     if (history.equipmentSerial != null) {
@@ -245,4 +245,4 @@ class InventoryHistoryService {
       ].any((field) => field.toLowerCase().contains(keyword));
     }).toList();
   }
-}
+}