refactor(ui-lvgl): Diagnostics > Noise is one measurement for any board

The Noise tab held the L2's interference hunt: parts of the board off one
by one, a slow cycle for a second radio, a spike hunt and three sweeps
(~90 s, L2 only). It is now one Measure: the noise floor on the mesh
frequency (median and 10th percentile of 5 s) and a +-1.1 MHz sweep round
it, ~12 s, with a short legend for reading it. Works wherever the variant
defines the radio.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/companion_radio/ui-lvgl/UITask.h

@@ -278,8 +278,6 @@ public:
   void diagResetPopup();
   void diagReset();
   void diagNoiseRun();
-  void diagNoiseDetect();
-  void diagSpikeHunt();
   void showCompass();
   void favTap(int slot);
   void favHold(int slot);