Coupons README: request telemetry (telemetry_samples, one-minute aggregates, 14 days) (#64)

ddiff --git a/README.md b/README.md
iindex 1231fe2..316cb07 100644
---- a/README.md
++++ b/README.md
@@@ -52,6 +52,14 @@ Other tables in the same database:
  - `event_outbox`: the SDK transactional outbox.
  - `coupons_index_revisions`: the openvibe-publishing index sequencer.
  
++Request telemetry lives in this database too, in `telemetry_samples` (migration
++`0003_telemetry.sql`). Each HTTP request is aggregated by route template, method and status class,
++never by raw URL; once a minute `server/index.js` writes one `http.request` sample per key, plus
++the active-requests, p95 latency and event-loop-lag gauges (openvibe-sdk 0.46 telemetry, the
++`platform.telemetry-sample@1` shape), and deletes rows older than 14 days daily. `/shared` files,
++static assets, health, readiness and `/metrics` are not counted. `server/app.js` builds the
++collector (`createHttpTelemetry`) and mounts its middleware; the flush also runs on stop.
++
  Nothing is seeded, and no code, merchant or report is invented for a demo.
  
  ## Does not own