waterfall color designer app (#2625)

firmware/application/ui/ui_spectrum.cpp

@@ -332,6 +332,10 @@ WaterfallView::WaterfallView(const bool cursor) {
         }
     };
 
+    load_gradient();
+}
+
+void WaterfallView::load_gradient() {
     if (!waterfall_widget.gradient.load_file(default_gradient_file)) {
         waterfall_widget.gradient.set_default();
     }

firmware/application/ui/ui_spectrum.hpp

@@ -146,6 +146,7 @@ class WaterfallView : public View {
 
     void set_parent_rect(const Rect new_parent_rect) override;
     void show_audio_spectrum_view(const bool show);
+    void load_gradient();
 
    private:
     void update_widgets_rect();