feat(Core/UI): 백테스트 전역 엔진 선택 버튼 추가 및 스캘핑 Rust 방어로직 포팅 1차 완료

scratch/fix_surrogates.py

@@ -0,0 +1,12 @@
+with open("scratch/restore_backtest_safe.py", "r", encoding="utf-8") as f:
+    text = f.read()
+
+# Replace surrogate pairs with actual characters or proper escapes
+# \ud83c\udfc6 -> 🏆
+text = text.replace(r"\ud83c\udfc6", "🏆")
+# We also have \ube44 (비), \uad50 (교) etc, but those are just normal BMP characters,
+# but they might be encoded as surrogates? No, BMP is fine.
+
+with open("scratch/restore_backtest_safe.py", "w", encoding="utf-8") as f:
+    f.write(text)
+print("Fixed surrogates")