fix(swarm): Convert boolean env vars to strings in orchestrator service

Docker Compose/Swarm requires environment variables to be strings, not booleans.

Changes:
- KILLSWITCH_ENABLED: true -> "true"
- SANDBOX_ENABLED: true -> "true"

Fixes deployment error: 'must be a string, number or null'

docker-compose.swarm.yml

@@ -291,8 +291,8 @@ services:
       DOCKER_SOCKET: /var/run/docker.sock
       GIT_USER_NAME: "Mosaic Orchestrator"
       GIT_USER_EMAIL: "orchestrator@mosaicstack.dev"
-      KILLSWITCH_ENABLED: true
-      SANDBOX_ENABLED: true
+      KILLSWITCH_ENABLED: "true"
+      SANDBOX_ENABLED: "true"
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock:ro
       - orchestrator_workspace:/workspace