perf: move blocking homepage and hash I/O off loop

Co-authored-by: Copilot App <[email protected]>

tests/test_app.py

@@ -65,6 +65,7 @@ class TestAppLifespan:
             openrouter_api_key="test-key",
             environment="test",
             bootstrap_schema_on_startup=True,
+            worker_poll_interval_seconds=2.5,
             upload_dir=tmp_path / "uploads",
             prompt_dir=tmp_path / "prompts",
         )
@@ -80,6 +81,7 @@ class TestAppLifespan:
         assert "worker_start" in calls
         assert "worker_stop" in calls
         assert "dispose_db" in calls
+        assert worker_kwargs["poll_interval_seconds"] == pytest.approx(settings.worker_poll_interval_seconds)
         assert worker_kwargs["shutdown_timeout_seconds"] == pytest.approx(
             settings.worker_provider_timeout_seconds + settings.worker_shutdown_grace_seconds
         )