Deploy: fix the initdb race that made migrate time out

On a real Synology first run, `migrate` exited 1 with a bare asyncpg
TimeoutError while the postgres log showed a perfectly healthy server.

The healthcheck was `pg_isready` with no -h, so it checked the UNIX SOCKET.
During first-time initialisation the postgres image runs a temporary server
that listens on the socket only (listen_addresses=''), so pg_isready answered
and the container was marked healthy while nothing was listening on TCP yet.
Dependents then connected to postgres:5432, hung, and timed out. It only bites
on the very first start of a fresh data directory, which is exactly the run an
operator is doing when they have least idea what is wrong.

- healthcheck uses `pg_isready -h 127.0.0.1 -p 5432`, so health means TCP is
  actually accepting.
- `migrate` additionally waits for the port itself (DB_WAIT_SECONDS, default
  180) before running alembic. It is a one-shot with no restart policy, so a
  few seconds of slow NAS disk should not fail the whole bring-up; the API and
  workers already self-heal through their restart policy.

Verified with a first-time bring-up against a fresh data directory: migrate
logs "database accepting connections", applies core + all four plugin
branches, and the stack comes up serving.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nux3LCu4zP9nih4BRhPyHw

docker-compose.yml

@@ -136,7 +136,12 @@ services:
     volumes:
       - ${DATA_ROOT:-/NO-.env-FOUND-RUN-deploy_webmail.sh-init-FIRST}/postgres:/var/lib/postgresql/data
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-webmail} -d ${POSTGRES_DB:-webmail}"]
+      # -h 127.0.0.1 forces a TCP check. Without it pg_isready uses the Unix
+      # socket, which the temporary server that the postgres image runs during
+      # first-time initdb DOES answer (it listens on the socket only) — so the
+      # container went healthy before TCP was up, and dependents connecting to
+      # postgres:5432 hung until they timed out.
+      test: ["CMD-SHELL", "pg_isready -h 127.0.0.1 -p 5432 -U ${POSTGRES_USER:-webmail} -d ${POSTGRES_DB:-webmail}"]
       interval: 10s
       timeout: 5s
       retries: 12