refactor: migrate from SPIFFS to LittleFS for file handling

src/commonFS.h

@@ -2,11 +2,11 @@
 #define COMMONFS_H
 
 #include <Arduino.h>
-#include <SPIFFS.h>
 #include <ArduinoJson.h>
+#include <LittleFS.h>
 
 bool saveJsonValue(const char* filename, const JsonDocument& doc);
 bool loadJsonValue(const char* filename, JsonDocument& doc);
-void initializeSPIFFS();
+void initializeFileSystem();
 
 #endif