style: 채번규칙 카드 자체의 상하 패딩 제거

- Card 컴포넌트에 py-0 추가
- 카드 내부 여백 최소화

frontend/components/numbering-rule/NumberingRuleDesigner.tsx

@@ -251,7 +251,7 @@ export const NumberingRuleDesigner: React.FC<NumberingRuleDesignerProps> = ({
             savedRules.map((rule) => (
               <Card
                 key={rule.ruleId}
-                className={`border-border hover:bg-accent cursor-pointer transition-colors ${
+                className={`py-0 border-border hover:bg-accent cursor-pointer transition-colors ${
                   selectedRuleId === rule.ruleId ? "border-primary bg-primary/5" : "bg-card"
                 }`}
                 onClick={() => handleSelectRule(rule)}