feat: live agent answers (SSE streaming) + «Чат» tab on phones

- POST /dialog/{token}/events/stream: Server-Sent Events with the agent's steps («Смотрю вашу карту ЕМИАС…»,
  «Ищу в клинических рекомендациях…»), the answer as the model writes it (OpenRouter stream=true), then the
  final replies (same as /events, incl. the forbidden-output filter and sources). X-Accel-Buffering: no.
- Web: free-text messages use the stream — a live bubble with steps, typing dots and a cursor; falls back to
  the plain request if the stream breaks.
- Phones: the bottom tab bar gets «Чат» (it had no way back to the chat).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/screens/Messages.tsx

@@ -18,7 +18,7 @@ export function Messages() {
   useEffect(() => {
     dialog.markRead();
     endRef.current?.scrollIntoView({ block: "end" });
-  }, [dialog.entries.length]);
+  }, [dialog.entries.length, dialog.live?.text, dialog.live?.status.length]);
 
   const send = async (e?: FormEvent) => {
     e?.preventDefault();
@@ -56,6 +56,32 @@ export function Messages() {
               </li>
             ),
           )}
+          {dialog.live && (
+            <li className="bubble bubble--bot bubble--live" aria-busy="true">
+              <span className="bubble__avatar">
+                <Icon name="smile" size={20} />
+              </span>
+              <div className="live">
+                {dialog.live.status.map((st, i) => (
+                  <p key={i} className={`live__step${i === dialog.live!.status.length - 1 && !dialog.live!.text ? " is-active" : ""}`}>
+                    {st}
+                  </p>
+                ))}
+                {dialog.live.text ? (
+                  <p className="live__text">
+                    {dialog.live.text}
+                    <span className="live__cursor" aria-hidden="true" />
+                  </p>
+                ) : (
+                  <p className="live__dots" aria-label={t.typing}>
+                    <span />
+                    <span />
+                    <span />
+                  </p>
+                )}
+              </div>
+            </li>
+          )}
         </ol>
         {quick.length > 0 && (
           <div className="quickreplies">