feat(backend): Phase 1 数据层 — Domain / Provider / Failover 审计 + 持久化 + 同步 CLI

- domain：市场数据实体（Stock / 交易日历 / 日线 / 复权 / 财务含 announce_date）+ Repository 与 MarketDataProvider Protocol
- 数据源：TushareProvider（归一化、重试、鉴权错误归类）、SinaProvider（备用，明确前复权口径与能力边界）、FailoverProvider + SyncLog 审计（禁止静默切换）
- 持久化：SQLAlchemy 2.x Models + Repository 实现（按业务键幂等 upsert、as_of_date 防未来函数过滤）+ Alembic 迁移
- CLI：uv run python -m app.cli.sync {basic|calendar|daily|financial|verify}，支持 --resume 断点续传
- 真实 Tushare 验证：stock 5556 / 交易日历 366 / daily+factor 242 / 财务 55；sync_log 审计完整
- 测试：38 passed（domain / provider / failover / repository / 未来函数 / 迁移），ruff clean

backend/app/infrastructure/data_sources/failover.py

@@ -0,0 +1,179 @@
+"""Tushare → Sina Failover 包装（AGENT.md §7）。
+
+规则：
+- 优先 primary；primary 抛错时才尝试 fallback（避免对空结果做无谓兜底请求）
+- fallback 不支持该 API（DataSourceNotSupported）或自身失败 → 抛 DataSourceError
+- 每次尝试都写 SyncLog（source / 成功与否 / 行数 / 区间），禁止静默切换
+"""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from datetime import date
+from typing import Any
+
+from app.domain.entities.market import SyncLog
+from app.domain.providers import MarketDataProvider
+from app.infrastructure.data_sources.errors import DataSourceError, DataSourceNotSupported
+
+
+class FailoverProvider:
+    """以 primary 为主、fallback 为辅的 MarketDataProvider 实现。"""
+
+    name = "failover"
+
+    def __init__(
+        self,
+        primary: MarketDataProvider,
+        fallback: MarketDataProvider | None = None,
+        *,
+        audit: Callable[[SyncLog], None] | None = None,
+    ) -> None:
+        self.primary = primary
+        self.fallback = fallback
+        self._audit = audit or (lambda _log: None)
+
+    # ---- 各 API 代理 ----
+
+    def get_stock_basic(self) -> list:
+        return self._with_failover(
+            "get_stock_basic",
+            primary_call=lambda: self.primary.get_stock_basic(),
+            fallback_call=lambda: self.fallback.get_stock_basic(),
+        )
+
+    def get_trade_cal(self, start: date, end: date) -> list:
+        return self._with_failover(
+            "get_trade_cal",
+            start=start,
+            end=end,
+            primary_call=lambda: self.primary.get_trade_cal(start, end),
+            fallback_call=lambda: self.fallback.get_trade_cal(start, end),
+        )
+
+    def get_daily(self, symbol: str, start: date, end: date) -> list:
+        return self._with_failover(
+            "get_daily",
+            start=start,
+            end=end,
+            primary_call=lambda: self.primary.get_daily(symbol, start, end),
+            fallback_call=lambda: self.fallback.get_daily(symbol, start, end),
+        )
+
+    def get_adjust_factor(self, symbol: str, start: date, end: date) -> list:
+        return self._with_failover(
+            "get_adjust_factor",
+            start=start,
+            end=end,
+            primary_call=lambda: self.primary.get_adjust_factor(symbol, start, end),
+            fallback_call=lambda: self.fallback.get_adjust_factor(symbol, start, end),
+        )
+
+    def get_financial(self, symbol: str) -> list:
+        return self._with_failover(
+            "get_financial",
+            primary_call=lambda: self.primary.get_financial(symbol),
+            fallback_call=lambda: self.fallback.get_financial(symbol),
+        )
+
+    # ---- 内部 ----
+
+    def _with_failover(
+        self,
+        api: str,
+        *,
+        primary_call: Callable[[], list],
+        fallback_call: Callable[[], list] | None = None,
+        start: date | None = None,
+        end: date | None = None,
+    ) -> list:
+        try:
+            rows = primary_call()
+        except Exception as exc:  # noqa: BLE001 —— 统一走审计
+            self._log(
+                source=self.primary.name,
+                api=api,
+                success=False,
+                reason=str(exc),
+                start=start,
+                end=end,
+            )
+            return self._try_fallback(api, fallback_call, start=start, end=end, primary_error=exc)
+        self._log(
+            source=self.primary.name,
+            api=api,
+            success=True,
+            row_count=_len(rows),
+            start=start,
+            end=end,
+        )
+        return rows
+
+    def _try_fallback(self, api, fallback_call, *, start, end, primary_error):
+        if fallback_call is None or self.fallback is None:
+            raise DataSourceError(
+                f"{self.primary.name}.{api} 失败且无备用源: {primary_error}"
+            ) from primary_error
+        try:
+            rows = fallback_call()
+        except DataSourceNotSupported as exc:
+            self._log(
+                source=self.fallback.name,
+                api=api,
+                success=False,
+                reason=f"不支持: {exc}",
+                start=start,
+                end=end,
+            )
+            raise DataSourceError(
+                f"{self.primary.name}.{api} 失败，备用源不支持: {primary_error}"
+            ) from primary_error
+        except Exception as exc:  # noqa: BLE001
+            self._log(
+                source=self.fallback.name,
+                api=api,
+                success=False,
+                reason=str(exc),
+                start=start,
+                end=end,
+            )
+            raise DataSourceError(
+                f"主备数据源均失败: primary[{self.primary.name}]={primary_error} "
+                f"fallback[{self.fallback.name}]={exc}"
+            ) from exc
+        self._log(
+            source=self.fallback.name,
+            api=api,
+            success=True,
+            row_count=_len(rows),
+            start=start,
+            end=end,
+        )
+        return rows
+
+    def _log(
+        self,
+        *,
+        source: str,
+        api: str,
+        success: bool,
+        reason: str | None = None,
+        row_count: int = 0,
+        start: date | None = None,
+        end: date | None = None,
+    ) -> None:
+        self._audit(
+            SyncLog(
+                source=source,
+                api=api,
+                success=success,
+                failure_reason=reason,
+                row_count=row_count,
+                data_start=start,
+                data_end=end,
+            )
+        )
+
+
+def _len(rows: Any) -> int:
+    return len(rows) if rows is not None else 0