The telemetry dashboards' router/interface variables used a keep|distinct
Flux pattern that returned only one source; switch to schema.tagValues so all
streaming routers and interfaces are listed. Parameterize telegraf.conf gNMI
addresses and credentials via GNMI_ADDRESSES/GNMI_USERNAME/GNMI_PASSWORD so
the telemetry fleet can scale without editing the config.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>