refactor: 품목관리 시스템 리팩토링 및 Sales 페이지 추가

DynamicItemForm 개선:
- 품목코드 자동생성 기능 추가
- 조건부 표시 로직 개선
- 불필요한 컴포넌트 정리 (DynamicField, DynamicSection 등)
- 타입 시스템 단순화

새로운 기능:
- Sales 페이지 마이그레이션 (견적관리, 거래처관리)
- 공통 컴포넌트 추가 (atoms, molecules, organisms, templates)

문서화:
- 구현 문서 및 참조 문서 추가

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/components/items/DynamicItemForm/fields/DateField.tsx

@@ -1,100 +1,46 @@
 /**
- * DateField Component
- *
- * 날짜 선택 필드 (date, date-range)
+ * 날짜 입력 필드 컴포넌트
+ * 기존 ItemForm과 100% 동일한 디자인
  */
 
 'use client';
 
-import { useState } from 'react';
-import { format } from 'date-fns';
-import { ko } from 'date-fns/locale';
-import { CalendarIcon } from 'lucide-react';
-import { Button } from '@/components/ui/button';
-import { Calendar } from '@/components/ui/calendar';
 import { Label } from '@/components/ui/label';
-import {
-  Popover,
-  PopoverContent,
-  PopoverTrigger,
-} from '@/components/ui/popover';
-import type { DynamicFieldProps } from '../types';
-import { cn } from '@/lib/utils';
+import { Input } from '@/components/ui/input';
+import type { DynamicFieldRendererProps } from '../types';
 
 export function DateField({
   field,
   value,
-  error,
   onChange,
-  onBlur,
+  error,
   disabled,
-}: DynamicFieldProps) {
-  const [open, setOpen] = useState(false);
-
-  // 값을 Date 객체로 변환
-  const dateValue = value ? new Date(value as string) : undefined;
-  const isValidDate = dateValue && !isNaN(dateValue.getTime());
-
-  const handleSelect = (date: Date | undefined) => {
-    if (date) {
-      // ISO 문자열로 변환 (YYYY-MM-DD)
-      onChange(format(date, 'yyyy-MM-dd'));
-    } else {
-      onChange(null);
-    }
-    setOpen(false);
-    onBlur();
-  };
+}: DynamicFieldRendererProps) {
+  const fieldKey = field.field_key || `field_${field.id}`;
+  const stringValue = value !== null && value !== undefined ? String(value) : '';
 
   return (
-    <div className="space-y-2">
-      <Label
-        htmlFor={field.field_key}
-        className={cn(
-          'text-sm font-medium',
-          field.is_required && "after:content-['*'] after:ml-0.5 after:text-red-500"
-        )}
-      >
+    <div>
+      <Label htmlFor={fieldKey}>
         {field.field_name}
+        {field.is_required && <span className="text-red-500"> *</span>}
       </Label>
-
-      <Popover open={open} onOpenChange={setOpen}>
-        <PopoverTrigger asChild>
-          <Button
-            id={field.field_key}
-            variant="outline"
-            disabled={disabled || field.is_readonly}
-            className={cn(
-              'w-full justify-start text-left font-normal',
-              !isValidDate && 'text-muted-foreground',
-              error && 'border-red-500 focus:ring-red-500',
-              field.is_readonly && 'bg-gray-50 text-gray-500'
-            )}
-          >
-            <CalendarIcon className="mr-2 h-4 w-4" />
-            {isValidDate
-              ? format(dateValue, 'yyyy년 MM월 dd일', { locale: ko })
-              : field.placeholder || '날짜를 선택하세요'}
-          </Button>
-        </PopoverTrigger>
-        <PopoverContent className="w-auto p-0" align="start">
-          <Calendar
-            mode="single"
-            selected={isValidDate ? dateValue : undefined}
-            onSelect={handleSelect}
-            locale={ko}
-            initialFocus
-          />
-        </PopoverContent>
-      </Popover>
-
-      {field.help_text && !error && (
-        <p className="text-xs text-muted-foreground">{field.help_text}</p>
+      <Input
+        id={fieldKey}
+        type="date"
+        value={stringValue}
+        onChange={(e) => onChange(e.target.value)}
+        disabled={disabled}
+        className={error ? 'border-red-500' : ''}
+      />
+      {error && (
+        <p className="text-xs text-red-500 mt-1">{error}</p>
+      )}
+      {!error && field.description && (
+        <p className="text-xs text-muted-foreground mt-1">
+          * {field.description}
+        </p>
       )}
-
-      {error && <p className="text-xs text-red-500">{error}</p>}
     </div>
   );
 }
-
-export default DateField;