Phase 18: image prune (dangling/unused), local + agent (0.24.0)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/routers/agents.py

@@ -655,6 +655,26 @@ async def agent_image_check(
     return result
 
 
+@router.post("/{agent_id}/images/prune")
+async def agent_image_prune(
+    agent_id: int,
+    request: Request,
+    all_unused: bool = Query(False, alias="all"),
+    session: Session = Depends(get_session),
+    user: User = Depends(require_admin),
+) -> dict:
+    agent = _get_or_404(session, agent_id)
+    result = await _proxy(
+        session, agent, "POST", "/agent/images/prune", params={"all": all_unused}
+    )
+    audit_service.record(
+        session, user=user.username, action="agent.image.prune", target=agent.name,
+        detail=f"all={all_unused} reclaimed={(result or {}).get('SpaceReclaimed')}",
+        ip=_ip(request),
+    )
+    return result
+
+
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 # Volumes (proxied)
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