feat: add Ollama client and bounded request queue

backend/app/llm/client.py

@@ -0,0 +1,18 @@
+import httpx
+
+from app.config import settings
+
+
+class OllamaClient:
+    def __init__(self, base_url: str | None = None):
+        self._base_url = base_url or settings.ollama_base_url
+
+    async def generate(self, model: str, prompt: str, system: str | None = None) -> str:
+        payload = {"model": model, "prompt": prompt, "stream": False}
+        if system is not None:
+            payload["system"] = system
+
+        async with httpx.AsyncClient(base_url=self._base_url, timeout=120.0) as http_client:
+            response = await http_client.post("/api/generate", json=payload)
+            response.raise_for_status()
+            return response.json()["response"]