fix(deploy): add DATABASE_URL and openbrain network to orchestrator and synapse

Orchestrator was crashing with PrismaClientInitializationError because DATABASE_URL
was never added to docker-compose.swarm.portainer.yml when Prisma was integrated.
Synapse was failing because homeserver.yaml pointed to 'postgres' hostname instead
of the actual openbrain_brain-db service.

Changes:
- Add DATABASE_URL env var to orchestrator service
- Add openbrain_brain-internal network to orchestrator service
- Add openbrain_brain-internal network to synapse service

Note: homeserver.yaml /opt/mosaic/synapse/homeserver.yaml was also patched
directly on the server (host: postgres → host: openbrain_brain-db).

docker-compose.swarm.portainer.yml

@@ -316,6 +316,8 @@ services:
       SANDBOX_ENABLED: "true"
       # API key for authenticating requests from the web proxy
       ORCHESTRATOR_API_KEY: ${ORCHESTRATOR_API_KEY}
+      # Prisma database connection (uses the shared openbrain postgres)
+      DATABASE_URL: postgresql://${POSTGRES_USER}:${POSTGRES_PASSWORD}@openbrain_brain-db:5432/${POSTGRES_DB:-mosaic}
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock:ro
       - orchestrator_workspace:/workspace
@@ -331,6 +333,7 @@ services:
       start_period: 40s
     networks:
       - internal
+      - openbrain_brain-internal
     cap_drop:
       - ALL
     cap_add:
@@ -403,6 +406,7 @@ services:
     networks:
       - internal
       - traefik-public
+      - openbrain_brain-internal
     deploy:
       restart_policy:
         condition: on-failure