Scaffold Cloudron packaging workspace and automation

apps/sdrangel/README.md

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+# SDRAngel on Cloudron
+
+- **Upstream repository**: https://github.com/f4exb/sdrangel-docker
+- **Implementation issue**: https://projects.knownelement.com/issues/219
+- **Status**: Draft scaffolding generated on $(date -u +"%Y-%m-%dT%H:%M:%SZ")
+
+## Packaging Checklist
+
+1. Review upstream deployment requirements and map them to Cloudron services (database, cache, object storage, workers).
+2. Update `Dockerfile` with the correct build steps and runtime dependencies.
+3. Implement `start.sh` to configure the app from Cloudron-provided environment variables and launch the primary process.
+4. Edit `CloudronManifest.json` with accurate metadata, permissions, ports, addons, and health checks.
+5. Add integration and smoke tests under `test/` to validate the package.
+6. Document manual configuration steps, migration requirements, and known gaps in this README.
+
+## Notes
+
+- Replace the placeholder long-running process in `start.sh`.
+- Populate the `app/` directory with the application build artefacts or git submodules.
+- Use the shared packaging container (`docker/packager`) to run `cloudron build` and `cloudron install` so the host remains clean.