Add Airtime by Band, RF Spectrum and Signal Scope widgets for the NOC Builder

[bsnwgit]

Summary

Three Dashboard visuals had no NOC widget. This adds them:

• Airtime by Band — average channel utilization per band over time, across every radio (radio_trend covers one radio; channel_utilization is a ranking)
• RF Spectrum — each radio placed by channel and width in the 2.4, 5 and 6 GHz bands, height showing utilization; dashed marks a width that was not reported, an approximate position, or no utilization reading
• Signal Scope — every connected client by the access point it sits on, range showing signal strength

RF Spectrum and Signal Scope use app/wifi/rf.py, the same module as the Dashboard, so channel placement and signal thresholds cannot drift between the two. Signal Scope spreads clients around their sector with a stable hash (zlib.crc32), so the dots do not move between renders.

Notes

All new routes sit behind the existing suite-token dependency and take no request-supplied value other than the bounded time window.

Test plan

• All three load against live data; manifest lists them and pktHub's registry picked them up
• Rendered in pkthub's Dashboard, the NOC Builder canvas, and the public wall display page (RF Spectrum)

No automated tests: this repo has no tests/ folder.