chore: nest project under Arduino/WeatherPredictor

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

WeatherPredictor/state.h

@@ -1,15 +0,0 @@
-#pragma once
-#include "rtc_time.h"
-#include "forecast.h"
-
-struct AppState {
-  float    absHpa;
-  float    mslHpa;
-  float    tempC;
-  Trend    trend;
-  Forecast forecast;
-  RtcTime  now;
-  bool     haveTrend;
-};
-
-extern AppState g_state;