chore: make repo an Arduino collection with WeatherPredictor project

Flatten so the repo root is the Arduino sketchbook; the project lives in
WeatherPredictor/. Add a collection index README at the root and move the
detailed project README into WeatherPredictor/.

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

WeatherPredictor/net.cpp

@@ -0,0 +1,14 @@
+#include <ESP8266WiFi.h>
+#include <WiFiManager.h>
+#include "config.h"
+#include "net.h"
+
+bool netBegin() {
+  WiFiManager wm;
+  wm.setConfigPortalTimeout(180);         // give up portal after 3 min, run offline
+  bool ok = wm.autoConnect(AP_NAME);      // opens AP "WeatherPredictor-Setup" if no creds
+  return ok;
+}
+
+bool   netConnected() { return WiFi.status() == WL_CONNECTED; }
+String netIP()        { return WiFi.localIP().toString(); }