fix(supabase): add healthcheck to the meta service

[Carlos-Vera]

Problem

meta is the only service in the template without a healthcheck. Orchestrators that
colour a project by container health (EasyPanel, Portainer) therefore never show a
healthy stack as fully green, and a genuinely broken container is indistinguishable
from the one that simply never reports.

postgres-meta does declare a HEALTHCHECK in its own Dockerfile, but the published
images do not carry it — checked on both the version pinned here and the current
release:

$ docker buildx imagetools inspect supabase/postgres-meta:v0.96.6 --format '{{json .Image}}' | grep -o '"Healthcheck":[^,]*'
"Healthcheck":null
$ docker buildx imagetools inspect supabase/postgres-meta:v0.99.0 --format '{{json .Image}}' | grep -o '"Healthcheck":[^,]*'
"Healthcheck":null

So the compose file has to declare it.

Change

Adds the command postgres-meta declares in its own Dockerfile, on the port the
template already sets (PG_META_PORT: 8080).

Verification

Started meta v0.96.6 with PG_META_DB_HOST pointing at a host that does not resolve:

$ curl -s -o /dev/null -w '%{http_code}' http://localhost:8080/health
200
$ docker exec meta-test node -e "fetch('http://localhost:8080/health').then((r) => {if (r.status !== 200) throw new Error(r.status)})"
$ echo $?
0

/health answers 200 while the database is unreachable, so this tracks service
liveness and will not flap on a transient database blip — matching how the other
services in this file are checked.

Desarrollado por Carlos Vera para BravesLab con el favor de nuestro señor JesusCristo.