Raw counter and access passthroughs

GET /api/bng/counters                                  read_only
GET /api/bng/counters/{ip}                             read_only
GET /api/bng/access                                    read_only

These are thin proxies onto the corresponding controller endpoints, provided so
that a UI or script already talking to QuantumTouch does not need to change base
paths for the most frequently polled reads. The response bodies are the
controller's own and are documented in the companion BNG Telemetry API — the
node-wide QoS band aggregate, the per-subscriber band breakdown, and the enabled
access interfaces respectively.

The node-wide /counters read is cached for one second so that multiple
dashboard tabs share a single upstream request. The per-IP read is deliberately
uncached, because per-subscriber polling happens in a single drilldown view
where a stale rate would be misleading. /access is cached for thirty seconds.

For any controller endpoint not in this short list, use the /v1/* passthrough.

Time Series and Analytics

Retention is the operational plane's distinctive contribution. The controller
returns current state and cumulative totals; QuantumTouch retains history and
serves it back as queryable series.