docs: harden VPS install defaults

docs/vps.md

@@ -1,5 +1,5 @@
 ---
-summary: "VPS hosting hub for Clawdbot (Railway/Fly/Hetzner/exe.dev)"
+summary: "VPS hosting hub for Clawdbot (Fly/Hetzner/GCP/exe.dev)"
 read_when:
   - You want to run the Gateway in the cloud
   - You need a quick map of VPS/hosting guides
@@ -11,7 +11,6 @@ deployments work at a high level.
 
 ## Pick a provider
 
-- **Railway** (one‑click + browser setup): [Railway](/railway)
 - **Fly.io**: [Fly.io](/platforms/fly)
 - **Hetzner (Docker)**: [Hetzner](/platforms/hetzner)
 - **GCP (Compute Engine)**: [GCP](/platforms/gcp)
@@ -24,6 +23,8 @@ deployments work at a high level.
 - The **Gateway runs on the VPS** and owns state + workspace.
 - You connect from your laptop/phone via the **Control UI** or **Tailscale/SSH**.
 - Treat the VPS as the source of truth and **back up** the state + workspace.
+- Secure default: keep the Gateway on loopback and access it via SSH tunnel or Tailscale Serve.
+  If you bind to `lan`/`tailnet`, require `gateway.auth.token` or `gateway.auth.password`.
 
 Remote access: [Gateway remote](/gateway/remote)  
 Platforms hub: [Platforms](/platforms)