fix: 리포트 관리 기간 검색 캘린더 팝오버 짤림 현상 수정

- absolute → fixed 포지셔닝으로 변경하여 부모 overflow 영향 제거
- 필터 버튼 중앙 기준으로 팝오버 위치 계산
- 뷰포트 경계(8px 여백) 보호 로직 추가
- datePopoverRef 추가로 캘린더 내부 클릭 시 팝오버 닫힘 방지

Made-with: Cursor

frontend/app/(main)/admin/screenMng/reportList/page.tsx

@@ -47,6 +47,7 @@ export default function ReportManagementPage() {
   const [tempStartDate, setTempStartDate] = useState<Date | undefined>(undefined);
   const [tempEndDate, setTempEndDate] = useState<Date | undefined>(undefined);
   const filterRef = useRef<HTMLDivElement>(null);
+  const datePopoverRef = useRef<HTMLDivElement>(null);
 
   const {
     reports,
@@ -70,7 +71,10 @@ export default function ReportManagementPage() {
 
   useEffect(() => {
     const handleClickOutside = (e: MouseEvent) => {
-      if (filterRef.current && !filterRef.current.contains(e.target as Node)) {
+      const target = e.target as Node;
+      const isInsideFilter = filterRef.current?.contains(target);
+      const isInsideDatePopover = datePopoverRef.current?.contains(target);
+      if (!isInsideFilter && !isInsideDatePopover) {
         setFilterOpen(false);
         setDatePopoverOpen(false);
       }
@@ -223,8 +227,21 @@ export default function ReportManagementPage() {
 
               {filterOpen && datePopoverOpen && (
                 <div
-                  className="absolute top-full right-0 z-50 mt-1.5 rounded-lg border border-gray-200 bg-white shadow-lg"
-                  onMouseDown={(e) => e.stopPropagation()}
+                  ref={datePopoverRef}
+                  className="fixed z-50 rounded-lg border border-gray-200 bg-white shadow-lg"
+                  style={(() => {
+                    const triggerRect = filterRef.current?.getBoundingClientRect();
+                    if (!triggerRect) return { top: 0, left: 0 };
+                    const popoverWidth = 620;
+                    const triggerCenter = triggerRect.left + triggerRect.width / 2;
+                    const top = triggerRect.bottom + 6;
+                    let left = triggerCenter - popoverWidth / 2;
+                    if (left < 8) left = 8;
+                    if (left + popoverWidth > window.innerWidth - 8) {
+                      left = window.innerWidth - popoverWidth - 8;
+                    }
+                    return { top, left };
+                  })()}
                 >
                   <div className="flex items-center justify-between border-b px-4 py-3">
                     <button