[SandObserver]

Summary

• Declare the network object once per source, sharing the key with a showIf on statProvider, adding an interface picker fed by an interfaces endpoint to the three remote copies.
• Add a throughput endpoint dispatched on statProvider; the view calls it whenever the source is not this machine, and keeps the cached /api/network-stats reading otherwise.
• Read Glances' bytes_recv_rate_per_sec, falling back to the window and its time_since_update for version 3.
• Read Beszel's b as the whole host's rate, and derive a per-interface rate from the ni totals.
• Derive Unraid's rate from the cumulative bytesReceived and bytesSent in metrics.network.
• Key each derived rate to when the counters were taken rather than when they were read, so a source that publishes on its own schedule is not read as idle between publications, and skip a window where a counter went backwards.
• Poll a remote source every ten seconds instead of every three, and render a dash until a rate exists.

Testing
All green, including the Docker build. Added 13 tests covering each source's shape, the version-3 fallback, rate derivation between records, a repeated record, a reset counter, both pickers, and the configuration failures.

Verified end to end through a container against a real Glances 4.5.6, a real Beszel hub, and Unraid's own API server. That run corrected the Beszel per-interface path: its records land once a minute, so polling faster compared a record with itself and reported zero traffic. Confirmed live: Glances rates tracking a quiet interface, Beszel's host-wide rate, a real per-interface rate holding steady between records, and Unraid counters becoming a rate on the second read.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.
• CHANGELOG.md updated under Unreleased if the change is user-visible.