feat: 初始化selected_text状态，确保应用启动时的状态一致性

streamlit_ocr_validator.py

@@ -47,7 +47,6 @@ def main():
     
     if 'selected_text' not in st.session_state:
         st.session_state.selected_text = None
-    
     if 'marked_errors' not in st.session_state:
         st.session_state.marked_errors = set()