Add µPaaS deployment setup for fsn1app1

- Add Docker HEALTHCHECK instruction probing /.well-known/healthcheck.json
  (30s interval, 5s timeout, 10s start period, 3 retries) for µPaaS
  container health verification
- Create deploy/README.md with full µPaaS app configuration reference
  (app name, repo URL, branch, env vars, volumes, ports, production config)
- Add Deployment section to README.md linking to deploy docs
- Add deploy/ to .dockerignore (docs not needed in build context)

README.md

@@ -125,6 +125,17 @@ See `config.example.yml` for all options with defaults.
 - **Metrics**: Prometheus
 - **Logging**: stdlib slog
 
+## Deployment
+
+Pixa is deployed via
+[µPaaS](https://git.eeqj.de/sneak/upaas) on `fsn1app1`
+(paas.datavi.be). Pushes to `main` trigger automatic builds and
+deployments. The Dockerfile includes a `HEALTHCHECK` that probes
+`/.well-known/healthcheck.json`.
+
+See [deploy/README.md](deploy/README.md) for the full µPaaS app
+configuration, volume mounts, and production setup instructions.
+
 ## TODO
 
 See [TODO.md](TODO.md) for the full prioritized task list.