feat(backend): F1-6 sprint2 #4 储值卡余额迁移 sandbox_replay (SCD2 时光机)

新建 sandbox_replay/balance_replay.py 模块,迁移 fdw_queries.get_member_balance,
fdw_queries 改 thin wrapper 保持 5 处现有调用(chat/coach/customer x2/task_manager)
透明兼容。

数据源 dim_member_card_account 是 SCD2 维度表(原生支持时光机),sandbox 改造
关键是替换 scd2_is_current=1 过滤为 scd2_start_time + scd2_end_time 时间过滤
(ref_date+1day 边界 = 当天结束时仍 active 的版本,timestamptz 比较稳定)。

双口径 UI 走查 PASS(member=2799207363643141 葛先生,SCD2 历史余额变化样本):
- 4a live(today=2026-05-05): 储值余额 ¥6,602
- 4b sandbox=2026-04-20: 储值余额 ¥18,080(差异 1.1w+,时光机效果显著)

unit test sprint1+sprint2 累计 24/24 PASS,无回归。

附带本次 sprint 2 触发的架构级登记:
- 新建 docs/_overview/architecture-evolution-backlog.md(DWD 孤立 + Core 中间件 +
  库重组,长远架构演进 backlog)
- F1-6-tasks.md 登记 #3 累计交易笔数推迟 Sprint 3(ETL 配合新增
  total_open_table_count,因现有 total_visit_count 实算 COUNT(settle_type IN (1,3))
  含商城订单,不符 Neo "开台次数"业务语义)
- sandbox-replay-engine-spec §5.5 thin wrapper 决策原则(已在 #2 commit)

详见 docs/audit/changes/2026-05-06__f1_6_sprint2_member_balance.md

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/backend/app/services/sandbox_replay/__init__.py

@@ -32,6 +32,9 @@ F1-6 沙箱时光机阶段 B 启动模块。
 """
 
 from app.services.sandbox_replay._decorator import runtime_aware
+from app.services.sandbox_replay.balance_replay import (
+    get_member_balance as get_member_balance_replay,
+)
 from app.services.sandbox_replay.consumption_replay import (
     get_consumption_60d as get_consumption_60d_replay,
     get_last_visit_days as get_last_visit_days_replay,
@@ -43,4 +46,5 @@ __all__ = [
     "get_last_visit_days_replay",
     "get_consumption_60d_replay",
     "get_total_consume_amount_replay",
+    "get_member_balance_replay",
 ]