Improve timestamp handling and event navigation

server/monlet_server/api/agents.py

@@ -6,6 +6,7 @@ from ..cursors import decode, encode
 from ..db import get_session
 from ..models import Agent as AgentModel
 from ..schemas import Agent, AgentsPage
+from ..timeutil import to_utc
 
 router = APIRouter()
 
@@ -15,7 +16,7 @@ def _to_schema(a: AgentModel) -> Agent:
         agent_id=a.agent_id,
         hostname=a.hostname,
         status=a.status,
-        last_seen_at=a.last_seen_at,
+        last_seen_at=to_utc(a.last_seen_at),
         features=a.features or {"push": False, "metrics": False},
         labels=a.labels or {},
     )