feat: 信标设备绑定 + 蓝牙模式管理 + 系统管理增强 + 数据导出

- 新增 DeviceBeaconBinding 模型，信标-设备多对多绑定 CRUD
- 蓝牙打卡模式批量配置/恢复正常模式 API
- 反向同步: 查询设备 BTMACSET 配置更新数据库绑定 (独立 session 解决事务隔离)
- 设备列表快捷操作弹窗修复 (fire-and-forget IIFE 替代阻塞轮询)
- 保存按钮防抖: 围栏/信标绑定保存点击后 disabled + 转圈防重复提交
- 审计日志中间件 + 系统配置/备份/固件 API
- 设备分组管理 + 告警规则配置
- 5个数据导出 API (CSV UTF-8 BOM)
- 位置热力图 + 告警条件删除 + 位置清理

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <noreply@hapi.run>

app/services/export_utils.py

@@ -0,0 +1,59 @@
+"""
+CSV Export Utilities - CSV 数据导出工具
+Shared helpers for streaming CSV responses.
+"""
+
+import csv
+import io
+from collections.abc import AsyncIterator, Sequence
+from datetime import datetime
+from typing import Any
+
+
+def _format_value(value: Any) -> str:
+    """Format a single value for CSV output."""
+    if value is None:
+        return ""
+    if isinstance(value, datetime):
+        return value.strftime("%Y-%m-%d %H:%M:%S")
+    if isinstance(value, bool):
+        return "是" if value else "否"
+    if isinstance(value, float):
+        return f"{value:.6f}" if abs(value) < 1000 else f"{value:.2f}"
+    if isinstance(value, (dict, list)):
+        import json
+        return json.dumps(value, ensure_ascii=False)
+    return str(value)
+
+
+def build_csv_content(
+    headers: list[str],
+    rows: Sequence[Any],
+    field_extractors: list[Any],
+) -> str:
+    """Build complete CSV string with BOM for Excel compatibility.
+
+    Args:
+        headers: Column header names (Chinese).
+        rows: ORM model instances or row tuples.
+        field_extractors: List of callables or attribute name strings.
+    """
+    buf = io.StringIO()
+    buf.write("\ufeff")  # UTF-8 BOM for Excel
+    writer = csv.writer(buf)
+    writer.writerow(headers)
+    for row in rows:
+        values = []
+        for ext in field_extractors:
+            if callable(ext):
+                values.append(_format_value(ext(row)))
+            else:
+                values.append(_format_value(getattr(row, ext, "")))
+        writer.writerow(values)
+    return buf.getvalue()
+
+
+def csv_filename(prefix: str) -> str:
+    """Generate a timestamped CSV filename."""
+    ts = datetime.now().strftime("%Y%m%d_%H%M%S")
+    return f"{prefix}_{ts}.csv"