feat: 13个统计/聚合API + 前端同步 + 待完成功能文档

API新增:
- GET /api/system/overview 系统总览(在线率/今日统计/表大小)
- GET /api/locations/stats 位置统计(类型分布/小时趋势)
- GET /api/locations/track-summary/{id} 轨迹摘要(距离/时长/速度)
- POST /api/alarms/batch-acknowledge 批量确认告警
- GET /api/attendance/report 考勤日报表(每设备每天汇总)
- GET /api/bluetooth/stats 蓝牙统计(类型/TOP信标/RSSI分布)
- GET /api/heartbeats/stats 心跳统计(活跃设备/电量/间隔分析)
- GET /api/fences/stats 围栏统计(绑定/进出状态/今日事件)
- GET /api/fences/{id}/events 围栏进出事件历史
- GET /api/commands/stats 指令统计(成功率/类型/趋势)

API增强:
- devices/stats: 新增by_type/battery_distribution/signal_distribution
- alarms/stats: 新增today/by_source/daily_trend/top_devices
- attendance/stats: 新增today/by_source/daily_trend/by_device

前端同步:
- 仪表盘: 今日告警/考勤/定位卡片 + 在线率
- 告警页: 批量确认按钮 + 今日计数
- 考勤页: 今日计数
- 轨迹: 加载后显示距离/时长/速度摘要
- 蓝牙/围栏/指令页: 统计面板

文档: CLAUDE.md待完成功能按优先级重新规划

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

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

app/routers/heartbeats.py

@@ -73,6 +73,99 @@ async def list_heartbeats(
     )
 
 
+@router.get(
+    "/stats",
+    response_model=APIResponse[dict],
+    summary="心跳统计 / Heartbeat statistics",
+)
+async def heartbeat_stats(
+    hours: int = Query(default=24, ge=1, le=168, description="统计时间范围(小时)"),
+    db: AsyncSession = Depends(get_db),
+):
+    """
+    心跳数据统计：总记录数、活跃设备数、平均电量、按设备心跳间隔分析。
+    Heartbeat stats: total, active devices, avg battery, interval analysis.
+    """
+    from app.config import now_cst
+    from app.models import Device
+    from datetime import timedelta
+
+    now = now_cst()
+    cutoff = now - timedelta(hours=hours)
+
+    # Total in range
+    total = (await db.execute(
+        select(func.count(HeartbeatRecord.id)).where(HeartbeatRecord.created_at >= cutoff)
+    )).scalar() or 0
+
+    # Unique devices with heartbeats in range
+    active_devices = (await db.execute(
+        select(func.count(func.distinct(HeartbeatRecord.device_id)))
+        .where(HeartbeatRecord.created_at >= cutoff)
+    )).scalar() or 0
+
+    # Total registered devices
+    total_devices = (await db.execute(select(func.count(Device.id)))).scalar() or 0
+
+    # Avg battery and signal in range
+    avg_result = await db.execute(
+        select(
+            func.avg(HeartbeatRecord.battery_level),
+            func.avg(HeartbeatRecord.gsm_signal),
+        ).where(HeartbeatRecord.created_at >= cutoff)
+    )
+    avg_row = avg_result.one()
+    avg_battery = round(float(avg_row[0]), 1) if avg_row[0] else None
+    avg_signal = round(float(avg_row[1]), 1) if avg_row[1] else None
+
+    # Per-device heartbeat count in range (for interval estimation)
+    # Devices with < expected heartbeats may be anomalous
+    per_device_result = await db.execute(
+        select(
+            HeartbeatRecord.device_id,
+            HeartbeatRecord.imei,
+            func.count(HeartbeatRecord.id).label("hb_count"),
+            func.min(HeartbeatRecord.created_at).label("first_hb"),
+            func.max(HeartbeatRecord.created_at).label("last_hb"),
+        )
+        .where(HeartbeatRecord.created_at >= cutoff)
+        .group_by(HeartbeatRecord.device_id, HeartbeatRecord.imei)
+        .order_by(func.count(HeartbeatRecord.id).desc())
+    )
+    device_intervals = []
+    anomalous_devices = []
+    for row in per_device_result.all():
+        hb_count = row[2]
+        first_hb = row[3]
+        last_hb = row[4]
+        if hb_count > 1 and first_hb and last_hb:
+            span_min = (last_hb - first_hb).total_seconds() / 60
+            avg_interval_min = round(span_min / (hb_count - 1), 1) if hb_count > 1 else 0
+        else:
+            avg_interval_min = 0
+        entry = {
+            "device_id": row[0], "imei": row[1],
+            "heartbeat_count": hb_count,
+            "avg_interval_minutes": avg_interval_min,
+        }
+        device_intervals.append(entry)
+        # Flag devices with very few heartbeats (expected ~12/h * hours)
+        if hb_count < max(1, hours * 2):
+            anomalous_devices.append(entry)
+
+    return APIResponse(data={
+        "period_hours": hours,
+        "total_heartbeats": total,
+        "active_devices": active_devices,
+        "total_devices": total_devices,
+        "inactive_devices": total_devices - active_devices,
+        "avg_battery_level": avg_battery,
+        "avg_gsm_signal": avg_signal,
+        "device_intervals": device_intervals[:20],
+        "anomalous_devices": anomalous_devices[:10],
+    })
+
+
 @router.post(
     "/batch-delete",
     response_model=APIResponse[dict],