feat(docker): CYCLONE_ADMIN_* env vars for backend

docker-compose.yml

@@ -41,6 +41,12 @@ services:
       CYCLONE_RELOAD: "0"
       # Absolute path inside the container; the named volume mounts at /data.
       CYCLONE_DB_URL: "sqlite:////data/cyclone.db"
+      # Bootstrap admin (required on first boot unless at least one user
+      # already exists). The ${VAR:?msg} syntax makes docker-compose refuse
+      # to start with a clear error if the env var isn't set in the host
+      # environment.
+      CYCLONE_ADMIN_USERNAME: ${CYCLONE_ADMIN_USERNAME:?CYCLONE_ADMIN_USERNAME is required on first boot}
+      CYCLONE_ADMIN_PASSWORD: ${CYCLONE_ADMIN_PASSWORD:?CYCLONE_ADMIN_PASSWORD is required on first boot (min 12 chars)}
     volumes:
       - cyclone-data:/data
     # The healthcheck in the Dockerfile hits /api/health. The frontend