feat: add digital clock input and time converter integration

src/containers/TimeConverter.tsx

@@ -4,7 +4,30 @@ import { DigitalClock } from './DigitalClock';
 import { useCurrentTime } from '../hooks/useCurrentTime';
 
 export function TimeConverter() {
+  const { currentTime, setCurrentTime } = useCurrentTime();
   const [useSystemTime, setUseSystemTime] = useState(false);
-  // When useSystemTime is true, both BerlinClock and DigitalClock are disabled.
-  return null;
+
+  const handleTimeChange = (newTime: Date) => {
+    setCurrentTime(newTime);
+  };
+
+  return (
+    <div>
+      <label>
+        <input
+          type="checkbox"
+          data-testid="use-system-time"
+          checked={useSystemTime}
+          onChange={(e) => setUseSystemTime(e.target.checked)}
+        />
+        Use system time
+      </label>
+      <BerlinClock enabled={!useSystemTime} />
+      <DigitalClock
+        enabled={!useSystemTime}
+        currentTime={currentTime}
+        onTimeChange={handleTimeChange}
+      />
+    </div>
+  );
 }