feat(WEB): 테이블 컬럼 표시/숨김 설정 기능 추가

- useColumnSettings 훅: 컬럼 가시성 토글 로직
- useTableColumnStore: Zustand 기반 컬럼 설정 영속화 (localStorage)
- ColumnSettingsPopover: 컬럼 설정 UI 컴포넌트
- UniversalListPage/IntegratedListTemplateV2에 컬럼 설정 통합

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

src/components/molecules/ColumnSettingsPopover.tsx

@@ -0,0 +1,73 @@
+'use client';
+
+import { Settings2, RotateCcw } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import { Checkbox } from '@/components/ui/checkbox';
+import {
+  Popover,
+  PopoverContent,
+  PopoverTrigger,
+} from '@/components/ui/popover';
+import type { ColumnWithVisibility } from '@/hooks/useColumnSettings';
+
+interface ColumnSettingsPopoverProps {
+  columns: ColumnWithVisibility[];
+  onToggle: (key: string) => void;
+  onReset: () => void;
+  hasHiddenColumns: boolean;
+}
+
+export function ColumnSettingsPopover({
+  columns,
+  onToggle,
+  onReset,
+  hasHiddenColumns,
+}: ColumnSettingsPopoverProps) {
+  return (
+    <Popover>
+      <PopoverTrigger asChild>
+        <Button variant="outline" size="sm" className="relative h-8 px-2">
+          <Settings2 className="h-4 w-4" />
+          <span className="hidden sm:inline ml-1">컬럼</span>
+          {hasHiddenColumns && (
+            <span className="absolute -top-1 -right-1 h-2 w-2 rounded-full bg-blue-500" />
+          )}
+        </Button>
+      </PopoverTrigger>
+      <PopoverContent align="end" className="w-56 p-3">
+        <div className="flex items-center justify-between mb-2">
+          <span className="text-sm font-medium">컬럼 표시 설정</span>
+          <Button
+            variant="ghost"
+            size="sm"
+            className="h-7 px-2 text-xs"
+            onClick={onReset}
+          >
+            <RotateCcw className="h-3 w-3 mr-1" />
+            초기화
+          </Button>
+        </div>
+        <div className="space-y-1 max-h-[300px] overflow-y-auto">
+          {columns.map((col) => (
+            <label
+              key={col.key}
+              className={`flex items-center gap-2 px-2 py-1.5 rounded text-sm cursor-pointer hover:bg-muted/50 ${
+                col.locked ? 'opacity-50 cursor-not-allowed' : ''
+              }`}
+            >
+              <Checkbox
+                checked={col.visible}
+                onCheckedChange={() => onToggle(col.key)}
+                disabled={col.locked}
+              />
+              <span>{col.label}</span>
+              {col.locked && (
+                <span className="text-xs text-muted-foreground ml-auto">고정</span>
+              )}
+            </label>
+          ))}
+        </div>
+      </PopoverContent>
+    </Popover>
+  );
+}