chore(audit): 2026-04-20 历史批次预审 + 文档同步 + .gitignore 修正

- 新增 docs/audit/changes/2026-04-20__historical-batch-pre-audit.md
  157 文件分批盘点审计（7 条主线 + 10 项高/中风险 + 2 份迁移 SQL DDL 清单）
- 补追 docs/audit/changes/2026-04-15__meituan-settle-core-sync.md
  原审计产物因 .gitignore 屏蔽长期未入仓，本次一并追回
- 刷新 docs/audit/audit_dashboard.md（33 条审计记录）
- .gitignore 白名单放行 docs/audit/changes/*.md 与 audit_dashboard.md
  同时屏蔽 changes/changes/ 嵌套误产物目录
- 新增 docs/specs/audit-gap-recovery/tasks.md
  扫描嵌套目录发现 96 份 D 类孤本（从未入过 git history），
  生成独立 PRD 供单开任务清理与补追
- 文档同步（高风险项）：
  - apps/backend/docs/API-REFERENCE.md (+69)
  - apps/miniprogram/README.md (+50)
  - apps/etl/connectors/feiqiu/docs/architecture/data_flow.md (+52/-2)
  - apps/etl/connectors/feiqiu/docs/architecture/system_overview.md (+5/-3)

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

.gitignore

@@ -13,7 +13,13 @@ logs/
 *.jsonl
 
 # ===== 审计文件 =====
-docs/audit/
+docs/audit/*
+# 白名单：允许追踪审计变更记录与仪表盘
+!docs/audit/changes/
+!docs/audit/changes/*.md
+!docs/audit/audit_dashboard.md
+# 嵌套误产物目录暂存本地，后续按 docs/specs/audit-gap-recovery/tasks.md 处理
+docs/audit/changes/changes/
 
 # ===== 运行时产出 =====
 export/