feat: db base + config tests

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

yunke-server/tests/conftest.py

@@ -0,0 +1,17 @@
+"""Shared pytest fixtures for the yunke-server test suite."""
+
+import pytest
+
+from app.config import get_settings
+
+
+@pytest.fixture(autouse=True)
+def reset_settings_cache():
+    """Ensure each test starts with a fresh Settings cache.
+
+    Tests that mutate env vars and call `get_settings()` must also clear the
+    `lru_cache` themselves; this fixture is a safety net that runs after every
+    test so a cached `Settings` from one test never leaks into the next.
+    """
+    yield
+    get_settings.cache_clear()