feat(email): wire listmonk-hc into deploy + dev override + hc ramp-cap

- deploy.sh/deploy-dev.sh: bring up listmonk-hc (upstream image, excluded from
  build); document the one-time listmonk_hc DB create + --install.
- docker-compose.dev.override.yml: dev-only override (committed) that drops the
  prod host-port bindings and pins dev's own postgres volume (dev-pgdata) via
  compose !override tags. deploy-dev ships it as docker-compose.override.yml so
  syncing the canonical compose to the shared host no longer breaks dev's
  api-postgres (port :5432 clash + volume switch). Discovered + fixed while
  validating listmonk-hc on dev.
- pw-hc-rampcap.sh: healthcare analogue of pw-listmonk-rampcap, ramps the
  listmonk_hc cap 100->1000/h off /etc/postfix/hc-warmup-start, fully
  independent of the trucking ramp/cap.

docker-compose.dev.override.yml

@@ -0,0 +1,17 @@
+# Dev-only overrides. Dev shares the host with prod and historically used its
+# own postgres data volume (dev-pgdata) and no host-port bindings. The canonical
+# (prod) compose uses api-pgdata + host ports; pin dev back to its own data and
+# drop the clashing host ports. !override replaces base lists.
+services:
+  api-postgres:
+    ports: !override []
+    volumes: !override
+      - dev-pgdata:/var/lib/postgresql/data
+  listmonk:
+    ports: !override []
+  listmonk-hc:
+    ports: !override []
+volumes:
+  dev-pgdata:
+    external: true
+    name: performancewest-dev_dev-pgdata