Stash radio settings per app (#1151)

* add a little Stash utility.
* add radio state RAII helper.
* first part of radio_state changes
* add radio_state_ to rest of apps
* fix freq_step and format
* fix unused ui_sigfrx: corrected sample rate, added back freq setting

firmware/application/apps/ui_nuoptix.hpp

@@ -33,6 +33,7 @@
 #include "message.hpp"
 #include "volume.hpp"
 #include "audio.hpp"
+#include "radio_state.hpp"
 
 #define NUOPTIX_TONE_LENGTH ((TONES_SAMPLERATE * 0.049) - 1)  // 49ms
 
@@ -54,6 +55,11 @@ class NuoptixView : public View {
         IMPROVISE
     };
 
+    TxRadioState radio_state_{
+        1750000 /* bandwidth */,
+        1536000 /* sampling rate */
+    };
+
     tx_modes tx_mode{IDLE};
 
     void transmit(bool setup);