Spring Boot server integration via Erupt — annotation-driven A2A server

Hi a2a-java team — opening this per `CONTRIBUTING_INTEGRATIONS.md` to propose a Spring Boot server integration in the **Server Integrations** list.

**Project**: [Erupt](https://github.com/erupts/erupt) — annotation-driven Spring Boot admin framework (Apache 2.0). The `erupt-ai` module shipped A2A protocol support in 1.14.3 (this week), built on LangChain4j 1.11.

**What it adds for the A2A ecosystem**:
- **Spring Boot 3 runtime** — complements the existing Quarkus reference impls and the wildfly-extras Jakarta EE one.
- **Zero-boilerplate AgentCards / AgentExecutors** — auto-registered from `@Erupt` and `@AiToolbox` annotations, no manual `@ApplicationScoped` producers required.
- **Built-in admin UI** for managing AgentCards, MCP servers, and per-role tool whitelists (`LLMRole`).

If the maintainers are open to it, happy to:
1. Send a PR adding Erupt to the Server Integrations list.
2. Extract the Spring Boot glue into a standalone integration module following the wildfly-extras pattern.
3. Submit a write-up for `COMMUNITY_ARTICLES.md` once the integration post is published.

Let me know which direction you prefer. Thanks!

— YuePeng (maintainer, Erupt)