docs: Add releases administration guide (#764)

Add comprehensive documentation for the release process including
version bumping, changelog generation, and deployment steps.

docs/guides/administration/releases.md

@@ -0,0 +1,28 @@
+# Releases
+
+## Creating a Release
+
+1. Create a new release on [GitHub](https://github.com/modelcontextprotocol/registry/releases) with a semver tag (e.g., `v1.3.9`)
+2. This triggers the [release workflow](.github/workflows/release.yml) which:
+   - Builds `registry` and `mcp-publisher` binaries for all platforms using GoReleaser
+   - Signs artifacts with cosign
+   - Generates SBOMs
+   - Builds and pushes container images to `ghcr.io/modelcontextprotocol/registry`
+
+## Deploying to Production
+
+1. Update `deploy/Pulumi.gcpProd.yaml` (e.g., through a PR or by pushing directly to main):
+   ```yaml
+   mcp-registry:imageTag: 1.3.9
+   ```
+2. The [deploy-production workflow](.github/workflows/deploy-production.yml) automatically deploys
+
+## Staging
+
+Staging auto-deploys from `main` via [deploy-staging.yml](.github/workflows/deploy-staging.yml). It always runs the latest `main` branch code.
+
+## Rollback
+
+To rollback production, update `deploy/Pulumi.gcpProd.yaml` to the previous version and push.
+
+**Note:** Rollbacks may not work as expected if the release included database migrations, since migrations are not automatically reversed.