新增 affiliate_dash 回调路由与幂等去重(阶段 5)

- POST /api/v1/open/affiliate-dash:验签 → 查任务(404 重试) → webhook_events 幂等闸门 → 状态同步
- migration 013:webhook_events(provider+event_id 唯一)
- task-repo findAffiliateDashTaskByOrder(仿 feifei 同构 SQL)
- notify-service:去重闸门在找到任务之后,任务未匹配不被 eventId 永久拦截
- typecheck + 212 测试通过;前置错误分支脚本验证通过

apps/backend/src/db/migrations/013_affiliate_dash_webhook_events.sql

@@ -0,0 +1,15 @@
+CREATE TABLE IF NOT EXISTS webhook_events (
+  id BIGSERIAL PRIMARY KEY,
+  provider TEXT NOT NULL,
+  event_id TEXT NOT NULL,
+  event_type TEXT NOT NULL DEFAULT '',
+  task_id BIGINT,
+  payload JSONB NOT NULL,
+  processed_at TIMESTAMPTZ NOT NULL,
+  created_at TIMESTAMPTZ NOT NULL
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_webhook_events_provider_event_id
+  ON webhook_events(provider, event_id);
+
+COMMENT ON TABLE webhook_events IS '第三方回调事件去重表（provider + event_id 唯一，幂等处理）';