Display beacon discovery metadata

[bburda]

Summary

Display beacon discovery metadata in the entity detail view when beacon plugins are active.

---

Proposed solution (optional)

• Show beacon metadata in entity detail section
• Fetch from GET /{entity_type}/{entity_id}/x-medkit-topic-beacon and /x-medkit-param-beacon
• Gracefully handle 404 when beacon plugins are not loaded
• Display as collapsible section alongside other vendor extension data

---

Additional context (optional)

Depends on sovd_web_ui#42 (client migration). Beacon discovery is a push-based entity enrichment mechanism via ROS 2 topics, available since v0.4.0.