* telemetry: sync the server module to go 1.26
The root module moved to go 1.26 but the telemetry server module, which
replaces seaweedfs with the repo root, stayed on 1.25.8, so go refuses
to build or test it until the directive catches up.
* telemetry: confirm a cluster after a week of reports, not two days
Two days of history still lets recurring CI and demo clusters into the
confirmed fleet: anything torn down and rebuilt across a UTC midnight
counts. Requiring seven distinct UTC days keeps the fleet charts and the
version/OS distributions to clusters that actually stay up; real
clusters qualify after their first week, and the fallback to all active
clusters while none is confirmed is unchanged.
telemetry: confirmed-cluster stats
Count a cluster as confirmed once it has reported on >=2 distinct UTC
days (per-cluster history makes this a length check). Version/OS
distributions in /api/stats are computed over confirmed clusters, so a
one-shot injected report can't appear in them; falls back to all active
clusters while no confirmed ones exist (fresh server). Adds the
seaweedfs_telemetry_confirmed_clusters gauge and a dashboard card.
Chris Lu