fix: await get_all() in registry router and align get_all key names

The /registry/agents endpoint was 500 on every call because
AgentRegistry.get_all() is async but was called without await.
Also aligns get_all() dict keys (name, domain) with what the router reads.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agent_service/routers/registry.py

@@ -31,7 +31,7 @@ async def list_agents():
     llm_router = get_llm_router()
     if registry is None:
         raise HTTPException(status_code=status.HTTP_503_SERVICE_UNAVAILABLE, detail='Registry not ready')
-    agents = registry.get_all()
+    agents = await registry.get_all()
     result = []
     for agent in agents:
         backend = 'ollama'