Realtime APIs migrated to a lower-latency edge store

The realtime layer was moved onto a low-latency edge store, co-located with the ingestion path.

1. All realtime APIs (current concurrent viewers, realtime breakdown, realtime graph) now fetch from the edge store.
2. The Data query service connects directly to the edge store using a dedicated query path, removing an extra hop for realtime data.
3. The analytics backend now focuses on historical and aggregated queries, freeing up capacity for reporting workloads.
4. Cuts realtime API latency and improves performance during traffic spikes on live streams.