Gateway v2.5.1

- Fixed first-run completion with native HTTPS: Apply stays loading while Gateway restarts, then navigates freshly to sign-in after TLS has settled.
- Hardened setup and installer coverage, including release-script expectations and SQL Explorer loading-state test races.
- Expanded Gateway AI documentation for installation, authentication, Cloudflare, registries, ClickHouse, and troubleshooting.
- Updated installation, node, capability, and database-connector documentation for browser-first setup and private connector bindings.
- Included installer terminal and certificate-guidance refinements introduced since v2.5.0.