fix: exclude resolved problems from new-in-24h metrics (0.9.7)

Dashboard and created_within_hours list only show open/acknowledged problems
created in the last 24 hours; closed items appear under resolved only.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/tests/test_dashboard.py

@@ -83,7 +83,7 @@ def test_dashboard_summary_top_and_problems_24h(client, db_session, jwt_headers)
     body = r.json()
     assert body["events_last_24h"] == 5
     assert body["problems_open"] == 1
-    assert body["problems_opened_24h"] == 2
+    assert body["problems_opened_24h"] == 1
     assert body["problems_resolved_24h"] == 1
     assert body["top_hosts"][0]["hostname"] == "web-01"
     assert body["top_hosts"][0]["count"] == 3