Store case light brightness in EEPROM (#17307)

Marlin/src/module/configuration_store.cpp

   void M710_report(const bool forReplay);
 #endif
 
+#define HAS_CASE_LIGHT_BRIGHTNESS (ENABLED(CASE_LIGHT_MENU) && DISABLED(CASE_LIGHT_NO_BRIGHTNESS))
+#if HAS_CASE_LIGHT_BRIGHTNESS
+  #include "../feature/caselight.h"
+#endif
+
 #pragma pack(push, 1) // No padding between variables
 
 typedef struct { uint16_t X, Y, Z, X2, Y2, Z2, Z3, Z4, E0, E1, E2, E3, E4, E5; } tmc_stepper_current_t;
     uint8_t extui_data[ExtUI::eeprom_data_size];
   #endif
 
+  //
+  // HAS_CASE_LIGHT_BRIGHTNESS
+  //
+  #if HAS_CASE_LIGHT_BRIGHTNESS
+    uint8_t case_light_brightness;
+  #endif
+
 } SettingsData;
 
 //static_assert(sizeof(SettingsData) <= E2END + 1, "EEPROM too small to contain SettingsData!");
     planner.recalculate_max_e_jerk();
   #endif
 
+  #if HAS_CASE_LIGHT_BRIGHTNESS
+    update_case_light();
+  #endif
+
   // Refresh steps_to_mm with the reciprocal of axis_steps_per_mm
   // and init stepper.count[], planner.position[] with current_position
   planner.refresh_positioning();
     #endif
 
     //
+    // Case Light Brightness
+    //
+    #if HAS_CASE_LIGHT_BRIGHTNESS
+      EEPROM_WRITE(case_light_brightness);
+    #endif
+
+    //
     // Validate CRC and Data Size
     //
     if (!eeprom_error) {
         }
       #endif
 
+      //
+      // Case Light Brightness
+      //
+      #if HAS_CASE_LIGHT_BRIGHTNESS
+        _FIELD_TEST(case_light_brightness);
+        EEPROM_READ(case_light_brightness);
+      #endif
+
       eeprom_error = size_error(eeprom_index - (EEPROM_OFFSET));
       if (eeprom_error) {
         DEBUG_ECHO_START();
   #endif
 
   //
+  // Case Light Brightness
+  //
+
+  #if HAS_CASE_LIGHT_BRIGHTNESS
+    case_light_brightness = CASE_LIGHT_DEFAULT_BRIGHTNESS;
+  #endif
+
+  //
   // Magnetic Parking Extruder
   //