feat(p9): thread purpose + persist consent receipt through OutboundService

Task S2.2: OutboundService.send gains an optional purpose, passes it to the broker,
and persists the returned consentReceiptRef on IiosOutboundCommand (new nullable
column, migration outbound-consent). RouteService.execute passes 'route_forward';
calendar reminders pass 'meeting_reminder'. CMP-DENY → command BLOCKED, no send.
2 tests: receipt recorded on allow, purpose-DENY blocks.

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

packages/iios-service/src/routing/route.service.ts

@@ -87,6 +87,8 @@ export class RouteService {
       binding.destinationRef ?? 'default',
       { text: preview.text ?? '' },
       `route:${decision.id}`,
+      binding.scopeId,
+      'route_forward',
     );
     await this.prisma.iiosRouteDecision.update({ where: { id: decision.id }, data: { executed: true, executedCommandId: cmd.id } });
   }