fix: harden owner bootstrap and auth persistence

.env.example

@@ -2,9 +2,7 @@ POSTGRES_DB=nexus
 POSTGRES_USER=nexus
 POSTGRES_PASSWORD=replace-with-a-strong-database-password
 JWT_KEY=replace-with-at-least-32-random-bytes
-OWNER_EMAIL=owner@example.com
-OWNER_PASSWORD=replace-with-at-least-14-characters
-OWNER_DISPLAY_NAME=Owner
+BOOTSTRAP_OWNER_EMAIL=owner@example.com
 OPENCLAW_BASE_URL=http://host.docker.internal:18789
 OPENCLAW_GATEWAY_TOKEN=
 OPENCLAW_GATEWAY_PASSWORD=