CI: use WATCHTOWER_HTTP_API_TOKEN secret name as set on the repo

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

AGENTS.md

@@ -93,7 +93,7 @@ make typecheck      # mypy
 - Deployment is CI-driven: pushing a `v*` tag makes Gitea Actions test, build, and push
   `desklock-gateway:{latest,tag}` to the registry and trigger Watchtower
   (`.gitea/workflows/build.yml`; needs `REGISTRY_USER`/`REGISTRY_PASSWORD`/
-  `WATCHTOWER_TOKEN` secrets). Plain pushes to `main` run lint + tests only. The
+  `WATCHTOWER_HTTP_API_TOKEN` secrets). Plain pushes to `main` run lint + tests only. The
   gateway deploys as part of the **`tatlock-ui` Portainer stack** —
   `system-admin-toj/containers/stacks/tatlock-ui.yml` (registered in `CONTAINERS.md`,
   port 8600). Stack updates go through the Portainer API on :8001 (JWT auth; recipe in