v0.5.0

Added

• Backend findings and snapshot API (ADR 0011). Agent state is now
  projected into typed AgentSnapshot values and served from the backend,
  alongside prioritized findings for unreachable, stale, drifting, unowned,
  heuristic, idle, and unattributed-usage conditions. The fleet page and
  per-agent Agent card consume this neutral API instead of deriving state from
  catalog annotations in the browser.
• Backend package rename and expanded role. The backend package is now
  @showcall/backstage-plugin-agent-catalog-backend; it continues to ingest
  catalog entities and now also exposes the agent-catalog HTTP plugin used by
  the fleet UI and external integrations.