Add NVS storage handler and integrate with main application logic

main/io/io.h

@@ -0,0 +1,20 @@
+#pragma once
+#include "freertos/FreeRTOS.h"
+#include "freertos/event_groups.h"
+
+class KVStorageHandler {
+public:
+  virtual ~KVStorageHandler() = default;
+
+  virtual void init(const EventGroupHandle_t& system_event_group) = 0;
+
+  // Store a key-value pair
+  virtual void put(const char*& key, const char*& value) = 0;
+
+  // Retrieve a value by key, returns nullptr if key not found
+  // The caller is responsible for freeing the returned memory
+  virtual char* get(const char*& key) const = 0;
+
+  // Delete a key-value pair
+  virtual void remove(const char*& key) = 0;
+};