chore: add env_file: stack.env to all compose services

Portainer git-stack deployments require an explicit env_file reference
in the compose file to load variables from the repo's stack.env.
Adds env_file: [stack.env] before every service-level environment:
block across all 10 stacks.

stacks/owncloud/docker-compose.yml

@@ -16,6 +16,8 @@ services:
         condition: service_healthy
       redis:
         condition: service_healthy
+    env_file:
+      - stack.env
     environment:
       - OWNCLOUD_DOMAIN=${OWNCLOUD_DOMAIN}
       - OWNCLOUD_DB_TYPE=mysql
@@ -44,6 +46,8 @@ services:
     container_name: owncloud_mariadb
     restart: unless-stopped
     networks: [owncloud]
+    env_file:
+      - stack.env
     environment:
       - MYSQL_ROOT_PASSWORD=${MYSQL_ROOT_PASSWORD}
       - MYSQL_USER=${OWNCLOUD_DB_USER}