feat(billing): 完成异步结算与请求执行闭环

统一任务成功、Attempt 与结算 Outbox 的事务边界，增加多实例安全结算、人工复核、请求幂等与执行租约。钱包决策使用九位精确金额，并通过审计保护约束保留流水事实；同时补充管理接口、指标与 PostgreSQL 集成测试。

apps/api/internal/store/wallet_reservation_test.go

@@ -132,6 +132,10 @@ RETURNING id::text`, "wallet-reservation-user-"+suffix, "wallet_reservation_"+su
 	}
 	t.Cleanup(func() {
 		cleanupCtx := context.Background()
+		_, _ = db.pool.Exec(cleanupCtx, `DELETE FROM gateway_wallet_transactions WHERE gateway_user_id = $1::uuid`, userID)
+		_, _ = db.pool.Exec(cleanupCtx, `
+DELETE FROM gateway_wallet_account_audit_guards
+WHERE account_id IN (SELECT id FROM gateway_wallet_accounts WHERE gateway_user_id = $1::uuid)`, userID)
 		_, _ = db.pool.Exec(cleanupCtx, `DELETE FROM gateway_users WHERE id = $1::uuid`, userID)
 		_, _ = db.pool.Exec(cleanupCtx, `DELETE FROM gateway_tenants WHERE id = $1::uuid`, tenantID)
 	})