Fix backup stack env for Portainer git deploy.

Remove compose ${VAR} overrides that blanked stack.env values and map KOPIA_REPOSITORY_PASSWORD in init-kopia; use hostname-only B2 endpoint.

stacks/backup/docker-compose.yml

@@ -16,13 +16,6 @@ services:
     networks: [backup, edge]
     env_file:
       - stack.env
-    environment:
-      - KOPIA_PASSWORD=${KOPIA_REPOSITORY_PASSWORD}
-      - TZ=${TZ}
-      - B2_BUCKET=${B2_BUCKET}
-      - B2_KEY_ID=${B2_KEY_ID}
-      - B2_APPLICATION_KEY=${B2_APPLICATION_KEY}
-      - B2_ENDPOINT=${B2_ENDPOINT}
     cap_add:
       - SYS_ADMIN
     security_opt:
@@ -58,8 +51,6 @@ services:
     networks: [backup]
     env_file:
       - stack.env
-    environment:
-      - TZ=${TZ}
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock:ro
       - /config/backup/dumps:/dumps