feat: multi-agent SIP with Redis session lockout

- SessionService: Redis-backed session lock/unlock/refresh with 1hr TTL
- AgentConfigService: queries Agent entity, caches per-member config
- Auth login: resolves agent config, locks Redis session, returns SIP credentials
- Auth logout: unlocks Redis session, Ozonetel logout, clears cache
- Auth heartbeat: refreshes Redis TTL every 5 minutes
- Added ioredis dependency

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/auth/auth.module.ts

@@ -1,9 +1,14 @@
 import { Module } from '@nestjs/common';
 import { AuthController } from './auth.controller';
 import { OzonetelAgentModule } from '../ozonetel/ozonetel-agent.module';
+import { PlatformModule } from '../platform/platform.module';
+import { SessionService } from './session.service';
+import { AgentConfigService } from './agent-config.service';
 
 @Module({
-    imports: [OzonetelAgentModule],
+    imports: [OzonetelAgentModule, PlatformModule],
     controllers: [AuthController],
+    providers: [SessionService, AgentConfigService],
+    exports: [SessionService, AgentConfigService],
 })
 export class AuthModule {}