feat: BMP180 read and sea-level pressure conversion

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

WeatherPredictor/WeatherPredictor.ino

@@ -2,6 +2,7 @@
 #include <Wire.h>
 #include "config.h"
 #include "display_ui.h"
+#include "sensors.h"
 
 static void i2cScan() {
   Serial.println(F("I2C scan:"));
@@ -25,7 +26,14 @@ void setup() {
 
   displayBegin();
   displaySplash("Weather", "Predictor v0.1");
+
+  if (!sensorsBegin()) Serial.println(F("BMP180 not found!"));
 }
 
 void loop() {
+  float abs_ = readAbsPressureHpa();
+  float msl  = toSeaLevelHpa(abs_, DEFAULT_ALTITUDE_M);
+  Serial.printf("abs=%.1f hPa  msl=%.1f hPa  t=%.1f C\n",
+                abs_, msl, readTemperatureC());
+  delay(2000);
 }