Add deployment guide

docs/deployment-guide.md

@@ -0,0 +1,37 @@
+# Deployment Guide
+
+## Pre-flight checklist
+
+- [ ] All tests pass in CI
+- [ ] Release tag created in Git
+- [ ] Changelog updated
+- [ ] Rollback plan documented in the release ticket
+
+## Steps
+
+1. Pull the release artifact from S3:
+   ```
+   aws s3 cp s3://nexus-releases/<version>.tar.gz ./dist.tar.gz
+   tar -xzf dist.tar.gz -C ./dist/
+   ```
+
+2. Run the deploy script:
+   ```
+   ./scripts/deploy.sh <version>
+   ```
+
+3. Verify with health checks:
+   ```
+   ./scripts/health-check.sh
+   ```
+
+4. If anything fails, roll back immediately:
+   ```
+   ./scripts/rollback.sh
+   ```
+
+## Emergency contacts
+
+- On-call engineer: PagerDuty rotation
+- Infra lead: t.brenner@nexus.local
+- SRE: o.neumann@nexus.local