fix: 加固聊天限流与安全策略串行化

apps/api/src/safety/safety-lock.service.ts

@@ -0,0 +1,28 @@
+import { Injectable } from "@nestjs/common";
+import { type Prisma } from "@prisma/client";
+
+/**
+ * Transaction-scoped serialization protocol for policy subjects.
+ *
+ * Every transaction that reads or writes block, sanction, or account-status
+ * policy MUST call this method first for every affected account. IDs are
+ * de-duplicated and sorted so overlapping multi-account operations cannot
+ * deadlock. The lock is released by PostgreSQL only when the transaction ends;
+ * callers must therefore pass the transaction client, never PrismaService.
+ */
+@Injectable()
+export class SafetyLockService {
+  async lockAccounts(
+    tx: Prisma.TransactionClient,
+    accountIds: readonly string[],
+  ): Promise<void> {
+    const canonicalIds = Array.from(new Set(accountIds)).sort();
+    for (const accountId of canonicalIds) {
+      await tx.$executeRaw`
+        SELECT pg_advisory_xact_lock(
+          hashtextextended(${`safety:${accountId}`}, 0)
+        )
+      `;
+    }
+  }
+}