Remove dead _previous_frequency state from BigFrequency widget (#3294)

* Initial plan

* Remove unused _previous_frequency member from BigFrequency and remove paint() guard

Co-authored-by: gullradriel <3157857+gullradriel@users.noreply.github.com>

* Move frequency dirty-check to set() to avoid redundant repaints

Co-authored-by: gullradriel <3157857+gullradriel@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: gullradriel <3157857+gullradriel@users.noreply.github.com>

firmware/common/ui_widget.cpp

@@ -564,16 +564,14 @@ void LiveDateTime::set_seconds_enabled(bool new_value) {
 
 /* BigFrequency **********************************************************/
 
-BigFrequency::BigFrequency(
-    Rect parent_rect,
-    rf::Frequency frequency)
-    : Widget{parent_rect},
-      _frequency{frequency} {
-}
+BigFrequency::BigFrequency(Rect parent_rect, rf::Frequency frequency)
+    : Widget{parent_rect}, _frequency{frequency} {}
 
 void BigFrequency::set(const rf::Frequency frequency) {
+    if (_frequency != frequency) {
         _frequency = frequency;
         set_dirty();
+    }
 }
 
 void BigFrequency::paint(Painter& painter) {
@@ -583,9 +581,6 @@ void BigFrequency::paint(Painter& painter) {
     Point digit_pos;
     ui::Color segment_color;
 
-    if (_frequency != _previous_frequency) {
-        _previous_frequency = _frequency;
-
     rf::Frequency frequency{_frequency};
     const auto rect = screen_rect();  // why not use screen_rect() directly for width, ...? it may be too small, but ...
 
@@ -641,7 +636,6 @@ void BigFrequency::paint(Painter& painter) {
             digit_pos += {digit_width, 0};
         }
     }
-    }
 }
 
 /* ProgressBar ***********************************************************/

firmware/common/ui_widget.hpp

@@ -297,7 +297,6 @@ class BigFrequency : public Widget {
 
    private:
     rf::Frequency _frequency;
-    rf::Frequency _previous_frequency{~0LL};
 
     static constexpr Dim digit_width = 32;