feat(notifications): add POST /refresh schedule response

Return shouldNotify and nextNotifications with a 10-minute lookahead
timestamp for the app schedule API.

src/routes/notifications.ts

@@ -7,6 +7,15 @@ notificationsRouter.get("/", (_req, res) => {
   res.json({ ok: true, resource: "notifications" });
 });
 
+notificationsRouter.post("/refresh", async (_req, res) => {
+  const now = Date.now();
+
+  res.json({
+    shouldNotify: true,
+    nextNotifications: [{ timestamp: now + 600000 }],
+  });
+});
+
 notificationsRouter.post("/register", async (req, res) => {
   const { fcmToken, platform, testMode } = req.body as {
     fcmToken?: unknown;