test(ebook): cover protected phrases and migrate suite to async

Add test_protected_phrases.py covering phrase-matching behavior in the
RAG engine, and update the existing ebook_search tests to use the async
SQLAlchemy engine/session (create_async_engine, AsyncSession) and async
HTTP paths.

tests/ebook_search/test_health.py

@@ -5,7 +5,7 @@ from __future__ import annotations
 from typing import TYPE_CHECKING
 
 from fastapi.testclient import TestClient
-from sqlalchemy import create_engine
+from sqlalchemy.ext.asyncio import create_async_engine
 
 from python.ebook_search.api.main import create_app
 from python.ebook_search.config import EbookSearchConfig, RerankConfig
@@ -18,18 +18,18 @@ if TYPE_CHECKING:
 
 def fake_get_postgres_engine(**_kwargs):
     """Return an in-memory engine for route tests."""
-    return create_engine("sqlite+pysqlite:///:memory:", future=True)
+    return create_async_engine("sqlite+aiosqlite:///:memory:")
 
 
 def patch_app_runtime(mocker: MockerFixture):
-    mocker.patch("python.ebook_search.api.main.get_postgres_engine", side_effect=fake_get_postgres_engine)
+    mocker.patch("python.ebook_search.api.main.get_async_postgres_engine", side_effect=fake_get_postgres_engine)
     mocker.patch("python.ebook_search.api.main.ensure_bm25_corpus", side_effect=lambda _session, _config: None)
 
 
 def patch_dependencies(mocker: MockerFixture, *, database=True, embedding=True, chat=True, bm25="ok"):
     mocker.patch(f"{HEALTH_MODULE}.check_database", side_effect=lambda _session: database)
-    mocker.patch(f"{HEALTH_MODULE}.check_embedding_endpoint", side_effect=lambda _config: embedding)
-    mocker.patch(f"{HEALTH_MODULE}.check_chat_endpoint", side_effect=lambda _config: chat)
+    mocker.patch(f"{HEALTH_MODULE}.check_embedding_endpoint", side_effect=lambda _client, _config: embedding)
+    mocker.patch(f"{HEALTH_MODULE}.check_chat_endpoint", side_effect=lambda _client, _config: chat)
     mocker.patch(f"{HEALTH_MODULE}.check_bm25_status", side_effect=lambda _config: bm25)