feat(service): P5.4 outbound sandbox sink + rate limit + inspector read endpoints

OutboundService: idempotent commands, per-(channelType,target) rate-limit bucket,
sandbox send (no network) + delivery attempts. POST /v1/adapters/:type/send +
GET inbound/outbound (session-auth). 55 tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-service/src/adapters/adapters.dto.ts

@@ -0,0 +1,7 @@
+import { IsObject, IsOptional, IsString } from 'class-validator';
+
+export class SendDto {
+  @IsString() target!: string;
+  @IsOptional() @IsObject() payload?: Record<string, unknown>;
+  @IsOptional() @IsString() idempotencyKey?: string;
+}