feat(backtest): add CLI command with auto data fetch and table output

- Created src/easy_tdx/backtest/cli.py with backtest command
- Supports --strategy-file to load Python strategy classes
- Supports --indicators to precompute technical indicators
- Supports --cash, --commission, --execution, --period, --adjust, --count options
- Supports json/table/csv output formats
- Auto-loads K-line data via get_mac_client()
- Registered backtest command in src/easy_tdx/cli/__init__.py
- Added tests/unit/test_backtest_cli.py with basic CLI tests

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_backtest_cli.py

@@ -0,0 +1,30 @@
+"""回测 CLI 命令测试。"""
+
+from __future__ import annotations
+
+from click.testing import CliRunner
+
+
+class TestBacktestCLI:
+    """测试回测 CLI 命令。"""
+
+    def test_help(self):
+        """测试 --help 显示帮助。"""
+        from easy_tdx.backtest.cli import backtest
+
+        runner = CliRunner()
+        result = runner.invoke(backtest, ["--help"])
+        assert result.exit_code == 0
+        assert "回测引擎" in result.output
+        assert "--strategy-file" in result.output
+        assert "--cash" in result.output
+        assert "--commission" in result.output
+
+    def test_missing_strategy_fails(self):
+        """测试不指定策略则失败。"""
+        from easy_tdx.backtest.cli import backtest
+
+        runner = CliRunner()
+        result = runner.invoke(backtest, ["SZ", "000001"])
+        assert result.exit_code == 1
+        assert "必须指定" in result.output or "错误" in result.output