feat(mp): Phase 2 功能补全 — SOS+推送+趋势图tooltip+家属安全存储

- index: 添加 SOS 紧急求助悬浮按钮（仅患者可见）
- alerts: 告警页面添加微信推送订阅 + critical 推送标识
- TrendChart: 添加触摸 tooltip 显示日期和数值
- family: edit_patient 改用 secureSet/secureGet 安全存储

apps/miniprogram/src/components/TrendChart/index.scss

@@ -45,3 +45,21 @@
   0% { background-position: 200% 0; }
   100% { background-position: -200% 0; }
 }
+
+// ── Tooltip ──
+
+.trend-tooltip {
+  position: absolute;
+  transform: translateX(-50%);
+  background: rgba(15, 23, 42, 0.9);
+  padding: 6px 12px;
+  border-radius: 6px;
+  white-space: nowrap;
+  pointer-events: none;
+  z-index: 10;
+}
+
+.trend-tooltip-text {
+  font-size: 12px;
+  color: #fff;
+}

apps/miniprogram/src/components/TrendChart/index.tsx

@@ -1,4 +1,4 @@
-import React, { useEffect, useRef, useCallback } from 'react';
+import React, { useEffect, useRef, useCallback, useState } from 'react';
 import { Canvas, View, Text } from '@tarojs/components';
 import Taro from '@tarojs/taro';
 import './index.scss';
@@ -41,6 +41,7 @@ export default React.memo(function TrendChart({
   height = 500,
 }: TrendChartProps) {
   const canvasRef = useRef<any>(null);
+  const [tooltip, setTooltip] = useState<{ date: string; value: number; x: number } | null>(null);
 
   const draw = useCallback(() => {
     const node = canvasRef.current;
@@ -150,6 +151,26 @@ export default React.memo(function TrendChart({
     ctx.restore();
   }, [data, referenceMin, referenceMax]);
 
+  const handleTouchStart = useCallback((e: any) => {
+    if (!data || data.length === 0 || !canvasRef.current) return;
+    const touch = e.touches[0];
+    const node = canvasRef.current;
+    const dpr = getDPR();
+    const x = touch.x;
+    const w = node.width / dpr;
+    const pad = { left: 45, right: 15 };
+    const cw = w - pad.left - pad.right;
+    const relX = x - pad.left;
+    const idx = Math.round((relX / cw) * (data.length - 1));
+    if (idx >= 0 && idx < data.length) {
+      setTooltip({
+        date: data[idx].date,
+        value: data[idx].value,
+        x: pad.left + (idx / Math.max(data.length - 1, 1)) * cw,
+      });
+    }
+  }, [data]);
+
   useEffect(() => {
     const query = Taro.createSelectorQuery();
     query
@@ -181,7 +202,18 @@ export default React.memo(function TrendChart({
         type='2d'
         id='trend-chart-canvas'
         style={{ width: '100%', height: '100%' }}
+        onTouchStart={handleTouchStart}
       />
+      {tooltip && (
+        <View
+          className='trend-tooltip'
+          style={{ left: `${tooltip.x}px`, top: '8px' }}
+        >
+          <Text className='trend-tooltip-text'>
+            {tooltip.date}: {tooltip.value}{unit ? ` ${unit}` : ''}
+          </Text>
+        </View>
+      )}
     </View>
   );
 });