feat(schedule): 검색 결과 없음 UI 추가 및 빈 상태 위치 개선

- PC: 검색 모드에서 결과 0개일 때 아무것도 안 나오던 문제 수정
  (돋보기 아이콘 + 검색어 표시), 검색 중 로딩 구분
- 모바일: 검색/날짜별 빈 상태를 아이콘 포함 디자인으로 통일
- 빈 상태/로딩을 일정 영역 기준으로 배치
  (PC: 상단 30% 지점, 모바일: 중앙)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/pages/mobile/schedule/Schedule.jsx

@@ -695,7 +695,7 @@ function MobileSchedule() {
         className="mobile-content"
         ref={isSearchMode && searchTerm && !showSuggestionsScreen ? scrollContainerRef : contentRef}
       >
-        <div className={`px-4 pb-4 ${isSearchMode && showSuggestionsScreen ? 'pt-0' : 'pt-4'}`}>
+        <div className={`px-4 pb-4 min-h-full flex flex-col ${isSearchMode && showSuggestionsScreen ? 'pt-0' : 'pt-4'}`}>
           {isSearchMode ? (
             showSuggestionsScreen ? (
               // 추천 검색어 화면
@@ -720,11 +720,19 @@ function MobileSchedule() {
             ) : !searchTerm ? (
               <div className="text-center py-8 text-gray-400">검색어를 입력하세요</div>
             ) : searchLoading ? (
-              <div className="flex justify-center py-8">
+              <div className="flex-1 flex items-center justify-center">
                 <div className="w-8 h-8 border-2 border-primary border-t-transparent rounded-full animate-spin" />
               </div>
             ) : searchResults.length === 0 ? (
-              <div className="text-center py-8 text-gray-400">검색 결과가 없습니다</div>
+              <div className="flex-1 flex flex-col items-center justify-center">
+                <div className="w-20 h-20 bg-gray-100 rounded-full flex items-center justify-center mb-3">
+                  <svg className="w-10 h-10 text-gray-300" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                    <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={1.5} d="M21 21l-4.35-4.35M11 18a7 7 0 110-14 7 7 0 010 14z" />
+                  </svg>
+                </div>
+                <p className="text-gray-400 text-base font-medium mb-1">검색 결과가 없습니다</p>
+                <p className="text-gray-300 text-sm">'<span className="text-gray-400">{searchTerm}</span>'에 대한 일정을 찾을 수 없습니다</p>
+              </div>
             ) : (
               <>
                 <div
@@ -771,12 +779,19 @@ function MobileSchedule() {
               </>
             )
           ) : loading ? (
-            <div className="flex justify-center py-8">
+            <div className="flex-1 flex items-center justify-center">
               <div className="w-8 h-8 border-2 border-primary border-t-transparent rounded-full animate-spin" />
             </div>
           ) : selectedDateSchedules.length === 0 ? (
-            <div className="text-center py-8 text-gray-400">
+            <div className="flex-1 flex flex-col items-center justify-center">
-              {selectedDate.getMonth() + 1}월 {selectedDate.getDate()}일 일정이 없습니다
+              <div className="w-20 h-20 bg-gray-100 rounded-full flex items-center justify-center mb-3">
+                <svg className="w-10 h-10 text-gray-300" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={1.5} d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5a2 2 0 00-2 2v12a2 2 0 002 2z" />
+                </svg>
+              </div>
+              <p className="text-gray-400 text-base font-medium">
+                {selectedDate.getMonth() + 1}월 {selectedDate.getDate()}일 일정이 없습니다
+              </p>
             </div>
           ) : (
             <div className="space-y-3">

frontend/src/pages/pc/public/schedule/Schedule.jsx

@@ -77,6 +77,7 @@ function PCSchedule() {
     fetchNextPage,
     hasNextPage,
     isFetchingNextPage,
+    isLoading: isSearchLoading,
   } = useInfiniteQuery({
     queryKey: ['scheduleSearch', searchTerm],
     queryFn: async ({ pageParam = 0 }) => {
@@ -546,7 +547,7 @@ function PCSchedule() {
             {/* 스케줄 목록 */}
             <div ref={scrollContainerRef} className="flex-1 min-h-0 overflow-y-auto space-y-4 py-2 pr-2">
               {loading ? (
-                <div className="text-center py-20 text-gray-500">로딩 중...</div>
+                <div className="h-full flex items-center justify-center text-gray-500">로딩 중...</div>
               ) : filteredSchedules.length > 0 ? (
                 isSearchMode && searchTerm ? (
                   <>
@@ -609,9 +610,26 @@ function PCSchedule() {
                     </motion.div>
                   ))
                 )
+              ) : isSearchMode && searchTerm ? (
+                isSearchLoading ? (
+                  <div className="h-full flex items-center justify-center text-gray-500">검색 중...</div>
+                ) : (
+                  <motion.div initial={{ opacity: 0, y: 10 }} animate={{ opacity: 1, y: 0 }} className="h-full flex flex-col items-center justify-start pt-[20%]">
+                    <div className="w-24 h-24 bg-gray-100 rounded-full flex items-center justify-center mb-4">
+                      <svg className="w-12 h-12 text-gray-300" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                        <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={1.5} d="M21 21l-4.35-4.35M11 18a7 7 0 110-14 7 7 0 010 14z" />
+                      </svg>
+                    </div>
+                    <p className="text-gray-400 text-lg font-medium mb-1">검색 결과가 없습니다</p>
+                    <p className="text-gray-300 text-sm">
+                      '<span className="text-gray-400">{searchTerm}</span>'
+                      {selectedCategories.length > 0 ? ' 검색 결과가 없습니다' : '에 대한 일정을 찾을 수 없습니다'}
+                    </p>
+                  </motion.div>
+                )
               ) : (
                 !isSearchMode && (
-                  <motion.div initial={{ opacity: 0, y: 10 }} animate={{ opacity: 1, y: 0 }} className="flex flex-col items-center justify-center py-16">
+                  <motion.div initial={{ opacity: 0, y: 10 }} animate={{ opacity: 1, y: 0 }} className="h-full flex flex-col items-center justify-start pt-[20%]">
                     <div className="w-24 h-24 bg-gray-100 rounded-full flex items-center justify-center mb-4">
                       <svg className="w-12 h-12 text-gray-300" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                         <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={1.5} d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5a2 2 0 00-2 2v12a2 2 0 002 2z" />