feat: modernize application — source, platform artifacts, CI/CD

- chore: ingest source code

108 files from https://github.com/spring-projects/spring-petclinic
- feat: add platform deployment artifacts
- feat: add CI/CD workflow automation

docs/architecture.md

@@ -0,0 +1,15 @@
+# Architecture
+
+## Service Design
+
+demo-fun-123 is a microservice following cloud-native patterns.
+
+## Technology Stack
+
+- **Runtime**: Java Spring Boot
+- **Deployment**: Humanitec Platform Orchestrator
+- **CI/CD**: Gitea Actions → ACR → Humanitec
+
+## Dependencies
+
+See `score.yaml` for external resource dependencies.