feat(data): read_parquet_15min + trader data_source(qfq/raw双源)

- datareader: +read_parquet_15min(sh/sz前缀+15min.parquet), get_database lazy(去tzlocal等依赖)
- data_source: iter_bars cross-section yield(date,{symbol:Bar}), raw首版fallback qfq+warning(spec§17)
- 本机 mock _read_fn 测调度逻辑, read_parquet_15min 容器冒烟 4 tests passed.

tests/trader/test_data_source.py

@@ -0,0 +1,58 @@
+"""data_source 测试（mock _read_fn，不依赖 vnpy 链，spec §5/§3.3）。
+
+read_parquet_15min 的真测试依赖 vnpy BarData + NAS parquet，本机无完整依赖，
+在容器内冒烟（spec §17）；本文件只测 iter_bars 调度逻辑。
+"""
+import logging
+from datetime import datetime
+from types import SimpleNamespace
+
+import pytest
+
+from sanguo_trader.data_source import iter_bars
+
+
+def _mock_bar(sym: str, date_str: str, close: float):
+    return SimpleNamespace(
+        symbol=sym,
+        datetime=datetime.strptime(date_str, "%Y-%m-%d"),
+        close_price=close,
+    )
+
+
+def test_iter_bars_cross_section_multi_symbol(monkeypatch):
+    def mock_read(sym, start, end, cfg):
+        return [_mock_bar(sym, "2024-01-02", 10.5 if sym == "600000" else 15.5)]
+    monkeypatch.setattr("sanguo_trader.data_source._read_fn", lambda iv: mock_read)
+    sections = list(iter_bars(["600000", "000001"], "2024-01-01", "2024-01-31", "d"))
+    assert len(sections) == 1
+    _date, d = sections[0]
+    assert "600000" in d and "000001" in d
+    assert d["600000"].close_price == 10.5
+
+
+def test_iter_bars_raw_fallback_warning(monkeypatch, caplog):
+    monkeypatch.setattr(
+        "sanguo_trader.data_source._read_fn",
+        lambda iv: lambda s, st, e, c: [],
+    )
+    with caplog.at_level(logging.WARNING):
+        list(iter_bars(["600000"], "2024-01-01", "2024-01-31", "d", adjust="raw"))
+    assert "raw" in caplog.text
+
+
+def test_unsupported_interval_rejected():
+    with pytest.raises(ValueError):
+        # _read_fn 在生成器首次 next 时才执行，用 list 触发
+        list(iter_bars(["600000"], "2024-01-01", "2024-01-31", "5m"))
+
+
+def test_fetch_day_returns_last_bar(monkeypatch):
+    from sanguo_trader.data_source import fetch_day
+    monkeypatch.setattr(
+        "sanguo_trader.data_source._read_fn",
+        lambda iv: lambda s, st, e, c: [_mock_bar(s, "2024-01-02", 10.0),
+                                        _mock_bar(s, "2024-01-02", 10.5)],
+    )
+    bar = fetch_day("600000", "2024-01-02", "d")
+    assert bar.close_price == 10.5   # 取最后一个