feat(bot): chat answers questions in any state; OpenRouter via proxy from the RF server

A question asked mid-questionnaire, mid-check-in or during a crisis is answered right away (agent →
guidelines/instruction); the pending question is re-shown with its buttons (engine remembers the last
prompt), in a crisis the answer carries the emergency contacts and the crisis stays open until the doctor's
ack. Acute messages still get the fixed crisis script. OpenRouter blocks RF IPs: OPENROUTER_PROXY_URL routes
the agent through an HTTP proxy, as vobot does.

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

app/llm/agent/providers.py

@@ -49,6 +49,7 @@ class OpenRouterProvider:
         self._model = settings.openrouter_model
         self._url = settings.openrouter_base_url.rstrip("/") + "/chat/completions"
         self._timeout = settings.chat_agent_timeout_s
+        self._proxy = settings.openrouter_proxy_url or None
         self._client = client
 
     async def chat(self, messages: list[dict[str, Any]], tools: list[dict[str, Any]]) -> AssistantTurn:
@@ -61,7 +62,7 @@ class OpenRouterProvider:
             if self._client is not None:
                 resp = await self._client.post(self._url, json=body, headers=headers, timeout=self._timeout)
             else:
-                async with httpx.AsyncClient(timeout=self._timeout) as client:
+                async with httpx.AsyncClient(timeout=self._timeout, proxy=self._proxy) as client:
                     resp = await client.post(self._url, json=body, headers=headers)
         except httpx.HTTPError as exc:
             raise ProviderError(type(exc).__name__) from exc