style: 채번규칙 카드 UI 개선

- '규칙 N개' 텍스트 제거 (불필요한 정보)
- 카드 내부 상하 여백 명시적으로 12px(py-3)로 설정

frontend/components/numbering-rule/NumberingRuleDesigner.tsx

@@ -256,11 +256,10 @@ export const NumberingRuleDesigner: React.FC<NumberingRuleDesignerProps> = ({
                 }`}
                 onClick={() => handleSelectRule(rule)}
               >
-                <CardHeader className="p-3">
+                <CardHeader className="px-3 py-3">
                   <div className="flex items-start justify-between">
                     <div className="flex-1">
                       <CardTitle className="text-sm font-medium">{rule.ruleName}</CardTitle>
-                      <p className="text-muted-foreground mt-1 text-xs">규칙 {rule.parts.length}개</p>
                     </div>
                     <Button
                       variant="ghost"
@@ -275,7 +274,7 @@ export const NumberingRuleDesigner: React.FC<NumberingRuleDesignerProps> = ({
                     </Button>
                   </div>
                 </CardHeader>
-                <CardContent className="p-3 pt-0">
+                <CardContent className="px-3 py-3 pt-0">
                   <NumberingRulePreview config={rule} compact />
                 </CardContent>
               </Card>