feat: add topic summarize endpoint

tests/test_api_topics.py

@@ -148,3 +148,58 @@ async def test_delete_topic(client):
 
     resp = await client.get(f"/api/topics/{topic_id}")
     assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_summarize_topic(client):
+    create_resp = await client.post(
+        "/api/topics",
+        json={"name": "summarize-test", "system_prompt": "You help."},
+    )
+    topic_id = create_resp.json()["data"]["id"]
+
+    from src.backend.db.database import get_db, create_request, complete_request
+
+    db = await get_db()
+    try:
+        req1 = await create_request(db, "Question 1", topic_id)
+        await complete_request(db, req1["id"], "Answer 1")
+        req2 = await create_request(db, "Question 2", topic_id)
+        await complete_request(db, req2["id"], "Answer 2")
+    finally:
+        await db.close()
+
+    from unittest.mock import patch, AsyncMock, MagicMock
+
+    mock_worker = MagicMock()
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {
+        "success": True,
+        "summary": "Comprehensive summary of all exchanges.",
+    }
+
+    mock_client = AsyncMock()
+    mock_client.post.return_value = mock_response
+    mock_client.__aenter__ = AsyncMock(return_value=mock_client)
+    mock_client.__aexit__ = AsyncMock(return_value=False)
+
+    with patch("src.backend.services.worker_client.httpx.AsyncClient", return_value=mock_client):
+        resp = await client.post(f"/api/topics/{topic_id}/summarize")
+
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["success"] is True
+    assert "summary" in data["data"]
+
+
+@pytest.mark.asyncio
+async def test_summarize_topic_no_requests(client):
+    create_resp = await client.post(
+        "/api/topics",
+        json={"name": "empty-topic", "system_prompt": "Empty."},
+    )
+    topic_id = create_resp.json()["data"]["id"]
+
+    resp = await client.post(f"/api/topics/{topic_id}/summarize")
+    assert resp.status_code == 400