refactor(concert): 세트리스트 회차 선택을 탭에서 드롭다운으로 변경

- 탭 UI → select 드롭다운 (회차가 많아도 깔끔)
- 드롭다운에 날짜 표시 (예: "1회차 (2026-04-01)")
- 회차 전환 시 애니메이션 제거
- framer-motion 의존성 제거

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/pc/admin/schedules/form/concert/SetlistSection.jsx

@@ -1,5 +1,4 @@
 import { useState, useRef, useEffect } from "react";
-import { motion, AnimatePresence } from "framer-motion";
 import { Plus, Trash2, Users, Search, Copy } from "lucide-react";
 
 import ConfirmDialog from "@/components/pc/admin/common/ConfirmDialog";
@@ -229,36 +228,26 @@ function SetlistSection({ rounds, setlists, setSetlists, members, selectedMember
           )}
         </div>
 
-        {/* 회차 탭 (2개 이상일 때만) */}
+        {/* 회차 선택 드롭다운 (2개 이상일 때만) */}
         {rounds.length > 1 && (
-          <div className="flex gap-1 mb-4 p-1 bg-gray-100 rounded-lg">
-            {rounds.map((round, index) => (
-              <button
-                key={round.id}
-                type="button"
-                onClick={() => setActiveRoundId(round.id)}
-                className={`flex-1 py-2 text-sm font-medium rounded-md transition-colors ${
-                  activeRoundId === round.id
-                    ? "bg-white text-primary shadow-sm"
-                    : "text-gray-500 hover:text-gray-700"
-                }`}
-              >
-                {index + 1}회차
-              </button>
-            ))}
+          <div className="mb-4">
+            <select
+              value={activeRoundId}
+              onChange={(e) => setActiveRoundId(Number(e.target.value))}
+              className="px-3 py-2 border border-gray-200 rounded-lg text-sm focus:outline-none focus:ring-2 focus:ring-primary focus:border-transparent"
+            >
+              {rounds.map((round, index) => (
+                <option key={round.id} value={round.id}>
+                  {index + 1}회차{round.date ? ` (${round.date})` : ''}
+                </option>
+              ))}
+            </select>
           </div>
         )}
 
         <div ref={containerRef} className="flex flex-col gap-4">
-          <AnimatePresence initial={false}>
             {setlist.map((song, index) => (
-              <motion.div
-                key={song.id}
-                initial={{ opacity: 0, scale: 0.98, y: -8 }}
-                animate={{ opacity: 1, scale: 1, y: 0 }}
-                exit={{ opacity: 0, scale: 0.98, y: -8 }}
-                transition={{ duration: 0.15, ease: "easeOut" }}
-              >
+              <div key={song.id}>
                 <div className="p-4 bg-gray-50 rounded-xl space-y-3">
                   {/* 헤더 */}
                   <div className="flex items-center justify-between">
@@ -349,9 +338,8 @@ function SetlistSection({ rounds, setlists, setSetlists, members, selectedMember
                     </div>
                   </div>
                 </div>
-              </motion.div>
+              </div>
             ))}
-          </AnimatePresence>
         </div>
 
         <div className="flex gap-2 mt-4">