Stop logging routine topology broadcasts

[nadaverell]

Summary

Avoid flooding Radar server logs with a success message on every debounced topology update. Topology broadcasts continue unchanged and remain observable through the existing SSE broadcast performance counter.

Testing

• make test
• make build
• Visual test skipped: no UI delta

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Note

Low Risk
Logging-only change with no behavior change to SSE delivery or topology build logic.

Overview
Removes the log.Printf that ran on every successful debounced topology broadcast in broadcastTopologyUpdate, which was flooding Radar server logs during normal operation.

SSE topology broadcasts are unchanged — clients still receive updates on the same debounce schedule. perfstats.IncSSEBroadcast() remains so broadcast volume stays visible via diagnostics/performance counters instead of log lines.

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