feat(web): service-worker notifications and composer/scroll UX fixes

- register notifications service worker and handle click-to-open chat/message

- route realtime notifications through service worker with fallback

- support ?chat=&message= deep-link navigation in chats page

- enforce 1s minimum voice message length

- lift scroll-to-bottom button to avoid overlap with composer action

web/public/notifications-sw.js

@@ -0,0 +1,33 @@
+self.addEventListener("install", (event) => {
+  event.waitUntil(self.skipWaiting());
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(self.clients.claim());
+});
+
+self.addEventListener("notificationclick", (event) => {
+  event.notification.close();
+  const data = event.notification.data || {};
+  const targetPath = typeof data.url === "string" ? data.url : "/";
+  const targetUrl = new URL(targetPath, self.location.origin).toString();
+
+  event.waitUntil(
+    self.clients.matchAll({ type: "window", includeUncontrolled: true }).then(async (clientList) => {
+      if (clientList.length > 0) {
+        const client = clientList[0];
+        if ("navigate" in client) {
+          await client.navigate(targetUrl);
+        }
+        if ("focus" in client) {
+          await client.focus();
+        }
+        return;
+      }
+      if (self.clients.openWindow) {
+        await self.clients.openWindow(targetUrl);
+      }
+    })
+  );
+});
+