feat: add apply button for date range - data loads only on click

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/page.tsx

@@ -23,8 +23,16 @@ export default function Home() {
   const defaultRange = getDefaultRange();
   const [startDate, setStartDate] = useState(defaultRange.start);
   const [endDate, setEndDate] = useState(defaultRange.end);
-  const { data, isLoading, error } = useReport(startDate, endDate);
+  const [appliedStart, setAppliedStart] = useState(defaultRange.start);
+  const [appliedEnd, setAppliedEnd] = useState(defaultRange.end);
+  const { data, isLoading, error } = useReport(appliedStart, appliedEnd);
   const reportRef = useRef<HTMLDivElement>(null);
+  const isDirty = startDate !== appliedStart || endDate !== appliedEnd;
+
+  const applyRange = () => {
+    setAppliedStart(startDate);
+    setAppliedEnd(endDate);
+  };
 
   const handleExportPdf = async () => {
     if (!reportRef.current) return;
@@ -113,6 +121,17 @@ export default function Home() {
               </button>
             ))}
           </div>
+          <button
+            onClick={applyRange}
+            disabled={!isDirty}
+            className={`px-4 py-1.5 text-sm rounded font-medium ${
+              isDirty
+                ? 'bg-blue-600 text-white hover:bg-blue-700'
+                : 'bg-gray-200 text-gray-400 cursor-not-allowed'
+            }`}
+          >
+            적용
+          </button>
         </div>
 
         <ErrorBoundary fallback="SummaryCards 오류">