feat(fe): Add form field navigation - Enter key moves to next field

- Create useFormFieldNavigation composable for Tab-like Enter behavior
- KsTextField: Enter -> next field
- KsTextArea: Ctrl+Enter for newline, Enter -> next field
- KsSelect: Enter -> next field after selection
- Implements standard form navigation pattern across input components

frontend/src/shared/shell/KsSidebar.vue

@@ -77,6 +77,15 @@ const menuItems: MenuItem[] = [
       { id: 'market-data', label: '시장 데이터 수집', icon: '💾', path: '/ops/market-data-ingestion' },
     ],
   },
+  {
+    id: 'system',
+    label: '시스템 설정',
+    icon: '⚙️',
+    path: '/system/common-codes',
+    children: [
+      { id: 'sys-common-codes', label: '공통코드 관리', icon: '🔤', path: '/system/common-codes' },
+    ],
+  },
   {
     id: 'ui-catalog',
     label: 'UI 컴포넌트 갤러리',
@@ -85,6 +94,7 @@ const menuItems: MenuItem[] = [
   },
 ]
 
+
 // Auto-expand sections based on current active route
 onMounted(() => {
   menuItems.forEach(item => {