Selfhosted: Missing dependencies in docker-compose.yaml

What needs fixing?

users-shard depends on postgres and nats but only has nats as dependency https://github.com/fluxerapp/fluxer/blob/main/deploy/self-hosting/docker-compose.yml#L312 app-proxy depends on postgres but only has API and Caddy as dependency https://github.com/fluxerapp/fluxer/blob/main/deploy/self-hosting/docker-compose.yml#L280 As somebody who was manually translating docker-compose.yaml into a quadlet for podman, these little things threw me off. Maybe they can cause small issues if services launch in wrong order on docker. Not a biggie but thought of referencing it here.

Adding postgres: {condition: service_healthy} to these two.