Add saved OLED controller selection on RAK boards

Allow Auto, SSD1306 or SH1106 through display.controller on display-enabled RAK4631 and RAK3401 roles. Persist the choice before restart without changing the active screen policy, and let saved Auto override legacy build defaults.

Share checked settings I/O and the existing atomic writer to keep Full Companion within its flash boundary while retaining features and existing record formats. Cover save failures, backup recovery, startup selection and ambiguous OLED replies.

Validation: 35 targeted host tests passed. RAK4631 Full Companion and RAK3401 unified LoRa OTA repeater build and package checks passed with release-length version strings.

examples/simple_sensor/main.cpp

@@ -5,6 +5,9 @@
 #include <helpers/IdentityGeneration.h>
 #include <helpers/ui/StartupScreen.h>
 #include <helpers/ui/DisplayPowerSettings.h>
+#if defined(OLED_AUTO_DETECT) && OLED_AUTO_DETECT
+#include <helpers/ui/OLEDControllerSettings.h>
+#endif
 #if defined(NRF52_PLATFORM)
   #include <helpers/nrf52/InternalPrimaryFsBoot.h>
   #include <helpers/nrf52/RamFallbackFileSystem.h>
@@ -174,6 +177,9 @@ void setup() {
   }
 #ifdef DISPLAY_CLASS
   mesh::ui::loadDisplayPowerSettings(fs, false);
+#if defined(OLED_AUTO_DETECT) && OLED_AUTO_DETECT
+  mesh::ui::loadOLEDControllerSettings(regulator_prefs_fs);
+#endif
   mesh::ui::StartupScreen startup_screen;
   display_ready = display.begin();
   if (display_ready) {