feat: 설정화면 생성

src/app/settings/page.tsx

@@ -0,0 +1,40 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+import { getPreferences, savePreferences } from '@/lib/store';
+
+export default function SettingsPage() {
+  const [hideSeconds, setHideSeconds] = useState(false);
+
+  useEffect(() => {
+    const prefs = getPreferences();
+    setHideSeconds(prefs.hideSeconds);
+  }, []);
+
+  const handleToggle = () => {
+    const newValue = !hideSeconds;
+    setHideSeconds(newValue);
+    savePreferences({ hideSeconds: newValue });
+  };
+
+  return (
+    <div className="p-6">
+      <h1 className="text-xl font-bold text-slate-100 mb-8">설정</h1>
+      
+      <div className="space-y-6">
+        <div className="flex items-center justify-between bg-slate-900/40 p-4 rounded-xl border border-slate-800">
+          <div>
+            <h3 className="font-medium text-slate-200">초 단위 숨기기</h3>
+            <p className="text-xs text-slate-500">타이머에서 분 단위만 표시하여 불안감을 줄입니다.</p>
+          </div>
+          <button 
+            onClick={handleToggle}
+            className={`w-12 h-6 rounded-full transition-colors relative ${hideSeconds ? 'bg-indigo-600' : 'bg-slate-700'}`}
+          >
+            <div className={`absolute top-1 w-4 h-4 rounded-full bg-white transition-transform ${hideSeconds ? 'left-7' : 'left-1'}`} />
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}