feat: Wi-Fi provisioning via WiFiManager captive portal

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

WeatherPredictor/WeatherPredictor.ino

@@ -7,6 +7,7 @@
 #include "forecast.h"
 #include "history.h"
 #include "app_settings.h"
+#include "net.h"
 #include "state.h"
 
 AppState g_state;
@@ -51,6 +52,13 @@ void setup() {
   historyLoad();   // restore prior samples (empty on first ever boot)
   Serial.printf("history restored: %d samples\n", historyCount());
 
+  displaySplash("WiFi", "Connect / portal");
+  if (netBegin()) {
+    Serial.printf("WiFi connected: %s\n", netIP().c_str());
+  } else {
+    Serial.println(F("WiFi not connected - running offline"));
+  }
+
   // Seed first sample immediately.
   sampleNow();
   historyAdd(rtcEpoch(), g_state.mslHpa, g_state.tempC);

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(); }

WeatherPredictor/net.h

@@ -0,0 +1,6 @@
+#pragma once
+#include <Arduino.h>
+
+bool   netBegin();
+bool   netConnected();
+String netIP();