feat: add memos stack (Coolify-ready)

- pull_policy: always on memos service
- hardcoded bind mounts: /opt/memos/{postgres,data}
- port hardcoded in label: 5230 (Gotcha 6)
- removed Portainer Traefik router labels (Coolify manages routing)
- removed traefik.enable / traefik.docker.network
- memos_internal: driver bridge (not fixed name)
- proxy: external: true

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

memos/stack.env

@@ -0,0 +1,5 @@
+TZ=Europe/Madrid
+MEMOS_DOMAIN=memos.sherlockhomeless.net
+MEMOS_DB_NAME=memos
+MEMOS_DB_USER=memos
+MEMOS_DB_PASSWORD=CAMBIAME_db_super_largo_y_unico