Restructure repository into output workspace

output/apps/seatunnel/README.md

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+# SeaTunnel on Cloudron
+
+- **Upstream repository**: https://github.com/apache/seatunnel
+- **Implementation issue**: https://projects.knownelement.com/issues/301
+- **Generated**: 2025-10-02T17:19:00Z UTC
+
+## Packaging Checklist
+
+1. Map upstream services (databases, caches, workers) to Cloudron addons; remove unused entries from `optionalAddons` and enable required ones under `addons`.
+2. Implement the multi-stage build in `Dockerfile` to fetch/compile the correct release of SeaTunnel.
+3. Update `start.sh` to configure the app from Cloudron environment variables and launch the primary process.
+4. Replace the placeholder health checks and smoke test with real coverage.
+5. Complete `CloudronManifest.json` (tagline, description, versioning, resource limits, ingress, TCP ports, etc.).
+6. Document manual configuration steps, migrations, and known gaps below.
+
+## Notes
+
+- Populate the `app/` directory with runtime overlays or artifacts generated during the build stage.
+- Use the shared packaging container (`output/docker/packager`) for `cloudron build/install` to keep the host clean.
+- Record decisions and operational requirements under `output/docs/apps/seatunnel/` as work progresses.