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/content/ru.ts

@@ -16,6 +16,7 @@ export const ru = {
     doctor: "Врач",
     profile: "Профиль",
     messages: "Сообщения",
+    chat: "Чат",
     signIn: "Вход",
     help: "Помощь",
   },
@@ -251,6 +252,7 @@ export const ru = {
     noticeTitle: "Опрос приостановлен",
   },
   messages: {
+    typing: "Помощник печатает",
     title: "Сообщения",
     inputLabel: "Сообщение",
     inputPlaceholder: "Напишите сообщение",