feat(center): add audit logs for auth and node operations

Fabric.Backend.Center/src/audit/audit.module.ts

@@ -0,0 +1,12 @@
+import { Global, Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { AuditLog } from '../entities/audit-log.entity';
+import { AuditService } from './audit.service';
+
+@Global()
+@Module({
+  imports: [TypeOrmModule.forFeature([AuditLog])],
+  providers: [AuditService],
+  exports: [AuditService],
+})
+export class AuditModule {}

Fabric.Backend.Center/src/audit/audit.service.ts

@@ -0,0 +1,31 @@
+import { Injectable } from '@nestjs/common';
+import { InjectRepository } from '@nestjs/typeorm';
+import { Repository } from 'typeorm';
+import { AuditLog } from '../entities/audit-log.entity';
+
+export type AuditWriteInput = {
+  action: string;
+  actorId?: string | null;
+  targetType?: string | null;
+  targetId?: string | null;
+  detail?: string | null;
+};
+
+@Injectable()
+export class AuditService {
+  constructor(
+    @InjectRepository(AuditLog)
+    private readonly auditRepo: Repository<AuditLog>,
+  ) {}
+
+  async write(input: AuditWriteInput): Promise<void> {
+    const row = this.auditRepo.create({
+      action: input.action,
+      actorId: input.actorId ?? null,
+      targetType: input.targetType ?? null,
+      targetId: input.targetId ?? null,
+      detail: input.detail ?? null,
+    });
+    await this.auditRepo.save(row);
+  }
+}