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/config.h

@@ -0,0 +1,37 @@
+#pragma once
+#include <Arduino.h>
+
+// ---- TFT (hardware SPI: SCK=D5, MOSI=D7) ----
+#define TFT_CS   D8
+#define TFT_DC   D3
+#define TFT_RST  D4
+#define TFT_BLK  D2
+
+// ---- I2C (BMP180 + DS3231 share this bus) ----
+#define I2C_SDA  D6
+#define I2C_SCL  D1
+#define BMP180_ADDR 0x77
+#define DS3231_ADDR 0x68
+
+// ---- Scheduler intervals (ms) ----
+// NOTE: for quick bench testing you may temporarily shrink these.
+static const unsigned long SAMPLE_INTERVAL_MS  = 60UL * 1000UL;         // read sensor / redraw
+static const unsigned long HISTORY_INTERVAL_MS = 5UL * 60UL * 1000UL;   // store a history sample
+static const unsigned long FLUSH_INTERVAL_MS   = 15UL * 60UL * 1000UL;  // flush history to flash
+
+// ---- History buffer ----
+static const int   HISTORY_SIZE        = 288;   // 24 h @ 5 min
+static const float TREND_THRESHOLD_HPA = 1.6f;  // >|1.6| hPa / 3 h = rising/falling
+
+// ---- Forecast change log ----
+static const int   FORECAST_LOG_SIZE   = 24;    // last N forecast changes
+
+// ---- Defaults (editable via web) ----
+static const float DEFAULT_ALTITUDE_M    = 150.0f;
+static const int   DEFAULT_TZ_OFFSET_MIN = 7 * 60; // UTC+7
+static const float DEFAULT_LAT           = 54.9870f;
+static const float DEFAULT_LON           = 82.8730f;
+
+// ---- Network ----
+// NTP is done by hard-coded IP in rtc_time.cpp (this LAN's DNS is unreliable).
+#define AP_NAME    "WeatherPredictor-Setup"