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/src/components/MessageList.tsx

@@ -494,11 +494,12 @@ export function MessageList() {
 
       <div className="px-5 pb-2 text-xs text-slate-300/80">{(typingByChat[activeChatId] ?? []).length > 0 ? "typing..." : ""}</div>
       {showScrollToBottom ? (
-        <div className="pointer-events-none absolute bottom-4 right-4 z-40">
+        <div className="pointer-events-none absolute bottom-20 right-4 z-40 md:bottom-24">
           <button
             className="pointer-events-auto inline-flex h-10 w-10 items-center justify-center rounded-full border border-slate-600/80 bg-slate-900/90 text-lg text-slate-100 shadow-lg hover:bg-slate-800"
             onClick={scrollToBottom}
             type="button"
+            title="Scroll to latest"
           >
             ↓
           </button>