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/pages/index/index.tsx

@@ -195,6 +195,35 @@ function GuestHome({ modeClass }: { modeClass: string }) {
 
 // ─── 登录后首页 ───
 
+function SOSButton() {
+  const user = useAuthStore((s) => s.user);
+  const isMedicalStaff = useAuthStore((s) => s.isMedicalStaff);
+  const currentPatient = useAuthStore((s) => s.currentPatient);
+
+  if (!user || !currentPatient || isMedicalStaff()) return null;
+
+  const handleSOS = async () => {
+    const { confirm } = await Taro.showModal({
+      title: '紧急求助',
+      content: '是否拨打急救电话？',
+      confirmText: '拨打',
+      cancelText: '取消',
+    });
+    if (confirm) {
+      Taro.makePhoneCall({
+        phoneNumber: '120',
+        fail: () => Taro.showToast({ title: '拨号失败', icon: 'none' }),
+      });
+    }
+  };
+
+  return (
+    <View className='sos-btn' onClick={handleSOS}>
+      <Text className='sos-btn-text'>SOS</Text>
+    </View>
+  );
+}
+
 function HomeDashboard({ modeClass }: { modeClass: string }) {
   const {
     healthItems, indicatorCapsules, completedCount, progressPercent,
@@ -302,6 +331,7 @@ function HomeDashboard({ modeClass }: { modeClass: string }) {
           <Text className='action-btn-text'>预约挂号</Text>
         </View>
       </View>
+      <SOSButton />
     </PageShell>
   );
 }