feat(01-01): add test scaffold, health and static asset tests, fix deprecated APIs

- requirements-dev.txt with pytest and httpx
- tests/conftest.py: client and tmp_data_dir fixtures
- tests/test_health.py: GET /health returns 200 with {"status": "ok"}
- tests/test_static.py: no CDN URLs in templates, dashboard returns 200
- Fix imptune/api/pages.py: use request= kwarg in TemplateResponse (Starlette compat)
- Fix imptune/main.py: replace deprecated on_event with asynccontextmanager lifespan

tests/conftest.py

@@ -0,0 +1,26 @@
+import os
+
+import pytest
+from fastapi.testclient import TestClient
+
+
+@pytest.fixture
+def client(tmp_data_dir):
+    from imptune.main import app
+
+    return TestClient(app)
+
+
+@pytest.fixture
+def tmp_data_dir(tmp_path, monkeypatch):
+    """Set DATA_DIR to a temp directory so tests don't write to /data."""
+    data_dir = tmp_path / "data"
+    data_dir.mkdir()
+    monkeypatch.setenv("DATA_DIR", str(data_dir))
+    # Patch config module so the app uses the temp dir
+    import imptune.config as cfg
+
+    cfg.DATA_DIR = str(data_dir)
+    cfg.DB_PATH = str(data_dir / "imptune.db")
+    cfg.DRIVERS_DIR = str(data_dir / "drivers")
+    return data_dir