fix: /admin 사이드바 검색 SQLite 연결 에러 해결

- /admin/search/user: new_connection=True + finally close
- /admin/search/product: new_connection=True + finally close
- 에러 로깅 강화 (traceback 포함)

backend/app.py

@@ -1416,10 +1416,10 @@ def admin_search_user():
     if not query:
         return jsonify({'success': False, 'message': '검색어를 입력하세요'}), 400
 
-    conn = db_manager.get_sqlite_connection()
-    cursor = conn.cursor()
-
+    conn = None
     try:
+        conn = db_manager.get_sqlite_connection(new_connection=True)
+        cursor = conn.cursor()
         if search_type == 'phone_last':
             # 전화번호 뒷자리 검색
             cursor.execute("""
@@ -1472,10 +1472,18 @@ def admin_search_user():
             })
 
     except Exception as e:
+        import traceback
+        logging.error(f"사용자 검색 실패: {e}\n{traceback.format_exc()}")
         return jsonify({
             'success': False,
             'message': f'검색 실패: {str(e)}'
         }), 500
+    finally:
+        if conn:
+            try:
+                conn.close()
+            except:
+                pass
 
 
 @app.route('/admin/search/product')
@@ -1486,10 +1494,10 @@ def admin_search_product():
     if not query:
         return jsonify({'success': False, 'message': '검색어를 입력하세요'}), 400
 
-    conn = db_manager.get_sqlite_connection()
-    cursor = conn.cursor()
-
+    conn = None
     try:
+        conn = db_manager.get_sqlite_connection(new_connection=True)
+        cursor = conn.cursor()
         # 1. MSSQL에서 제품명으로 거래번호 찾기
         session = db_manager.get_session('PM_PRES')
 
@@ -1560,10 +1568,18 @@ def admin_search_product():
         })
 
     except Exception as e:
+        import traceback
+        logging.error(f"제품 검색 실패: {e}\n{traceback.format_exc()}")
         return jsonify({
             'success': False,
             'message': f'검색 실패: {str(e)}'
         }), 500
+    finally:
+        if conn:
+            try:
+                conn.close()
+            except:
+                pass
 
 
 @app.route('/admin/ai-analyze-user/<int:user_id>', methods=['POST'])