fix: 移除 settings.DEBUG 引用，修复删除 DEBUG 字段后的启动报错

- database.py: echo 改为 False
- main.py: 错误响应直接显示异常信息（不再根据 DEBUG 判断）
- 机器人重复图片回复增加 OCR 识别内容展示

app/database.py

@@ -33,13 +33,13 @@ if IS_SQLITE:
 
     engine = create_async_engine(
         f"sqlite+aiosqlite:///{sqlite_path}",
-        echo=settings.DEBUG,
+        echo=False,
     )
 else:
     # PostgreSQL 配置
     engine = create_async_engine(
         DB_URL,
-        echo=settings.DEBUG,
+        echo=False,
         poolclass=NullPool,
         pool_pre_ping=True,
     )

app/main.py

@@ -208,7 +208,7 @@ async def global_exception_handler(request: Request, exc: Exception) -> JSONResp
     logger.error("未处理异常: %s", exc, exc_info=True)
     return JSONResponse(
         status_code=500,
-        content={"detail": "服务器内部错误", "message": str(exc) if settings.DEBUG else "请稍后重试"},
+        content={"detail": "服务器内部错误", "message": str(exc)},
     )