#12599: Fix gateway bind

<!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds a `start:zeabur` npm script intended for Zeabur deployments to run the gateway with an explicit bind mode (`--bind lan`) and a platform-provided port (`--port $PORT`), while skipping channel initialization via environment variables. Change is localized to `package.json` scripts and aligns with the existing `gateway:dev*` scripts that also set `OPENCLAW_SKIP_CHANNELS` / `CLAWDBOT_SKIP_CHANNELS`. <h3>Confidence Score: 4/5</h3> - This PR is likely safe to merge, with minor deployment-script portability concerns. - The change is a single added npm script; it doesn’t affect runtime code paths unless explicitly used. The main risk is the script’s use of `$PORT` without a default, which can fail on platforms that don’t set it or in Windows shells, but that’s limited to this opt-in script. - package.json <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->