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/services/device_service.py

@@ -289,12 +289,10 @@ async def batch_delete_devices(
 
 async def get_device_stats(db: AsyncSession) -> dict:
     """
-    获取设备统计信息 / Get device statistics.
+    获取设备统计信息（增强版）/ Get enhanced device statistics.
 
-    Returns
-    -------
-    dict
-        {"total": int, "online": int, "offline": int}
+    Returns dict with total/online/offline counts, online_rate,
+    by_type breakdown, battery/signal distribution.
     """
     total_result = await db.execute(select(func.count(Device.id)))
     total = total_result.scalar() or 0
@@ -303,11 +301,57 @@ async def get_device_stats(db: AsyncSession) -> dict:
         select(func.count(Device.id)).where(Device.status == "online")
     )
     online = online_result.scalar() or 0
-
     offline = total - online
 
+    # By device_type
+    type_result = await db.execute(
+        select(Device.device_type, func.count(Device.id))
+        .group_by(Device.device_type)
+        .order_by(func.count(Device.id).desc())
+    )
+    by_type = {row[0] or "unknown": row[1] for row in type_result.all()}
+
+    # Battery distribution: 0-20, 20-50, 50-100, unknown
+    from sqlalchemy import case
+    battery_result = await db.execute(
+        select(
+            func.sum(case((Device.battery_level < 20, 1), else_=0)).label("low"),
+            func.sum(case(((Device.battery_level >= 20) & (Device.battery_level < 50), 1), else_=0)).label("medium"),
+            func.sum(case((Device.battery_level >= 50, 1), else_=0)).label("high"),
+            func.sum(case((Device.battery_level.is_(None), 1), else_=0)).label("unknown"),
+        )
+    )
+    brow = battery_result.one()
+    battery_distribution = {
+        "low_0_20": int(brow.low or 0),
+        "medium_20_50": int(brow.medium or 0),
+        "high_50_100": int(brow.high or 0),
+        "unknown": int(brow.unknown or 0),
+    }
+
+    # Signal distribution: 0=none, 1-10=weak, 11-20=medium, 21-31=strong
+    signal_result = await db.execute(
+        select(
+            func.sum(case(((Device.gsm_signal.is_not(None)) & (Device.gsm_signal <= 10), 1), else_=0)).label("weak"),
+            func.sum(case(((Device.gsm_signal > 10) & (Device.gsm_signal <= 20), 1), else_=0)).label("medium"),
+            func.sum(case((Device.gsm_signal > 20, 1), else_=0)).label("strong"),
+            func.sum(case((Device.gsm_signal.is_(None), 1), else_=0)).label("unknown"),
+        )
+    )
+    srow = signal_result.one()
+    signal_distribution = {
+        "weak_0_10": int(srow.weak or 0),
+        "medium_11_20": int(srow.medium or 0),
+        "strong_21_31": int(srow.strong or 0),
+        "unknown": int(srow.unknown or 0),
+    }
+
     return {
         "total": total,
         "online": online,
         "offline": offline,
+        "online_rate": round(online / total * 100, 1) if total else 0,
+        "by_type": by_type,
+        "battery_distribution": battery_distribution,
+        "signal_distribution": signal_distribution,
     }