feat: API routes — speakers, rooms, search, RAG

Full implementations replacing stubs: speakers CRUD with utterance count,
rooms list + mute/unmute via pipeline, FTS5-based search, RAG /ask and
/summary endpoints. 15 route tests (8 new) all passing; 35 total.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/routes/test_rag.py

@@ -0,0 +1,21 @@
+def test_ask_returns_response(api_client, seeded_db, mocker):
+    mock_post = mocker.patch("app.api.routes.rag.httpx.post")
+    mock_post.return_value.json.return_value = {
+        "message": {"content": "You talked about groceries."}
+    }
+    mock_post.return_value.raise_for_status = lambda: None
+    room = seeded_db.execute("SELECT id FROM rooms WHERE name='Kitchen'").fetchone()
+    seeded_db.execute(
+        "INSERT INTO utterances (room_id, transcript, match_status, start_time, end_time) VALUES (?,?,?,?,?)",
+        (room["id"], "we need milk from the store", "unknown", "2026-01-01 10:00:00", "2026-01-01 10:00:03"),
+    )
+    seeded_db.commit()
+    resp = api_client.post("/api/ask", json={"question": "What did we need from the store?"})
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "answer" in data
+
+
+def test_get_summary_not_found(api_client):
+    resp = api_client.get("/api/summary/2026-01-01")
+    assert resp.status_code == 404