feat: phase 1 — data downloader, backtrader runner, SMA strategy

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_downloader.py

@@ -0,0 +1,18 @@
+import pytest
+from data.downloader import download_daily
+
+
+def test_download_single_stock():
+    """Smoke test: download data for 浦发银行 for a short window."""
+    df = download_daily("sh600000", "2024-01-01", "2024-01-31")
+    assert df is not None
+    assert len(df) > 0
+    assert list(df.columns) == ["symbol", "date", "open", "high", "low", "close", "volume", "amount"]
+    assert df["close"].notna().all()
+
+
+def test_download_baostock_fallback():
+    """Test baostock works as secondary source."""
+    df = download_daily("sz000001", "2024-06-01", "2024-06-15", source="baostock")
+    assert df is not None
+    assert len(df) > 0